Бауырлар және туыстық қатынастар

One of two or more individuals having at least one parent in common

A sibling is a relative that shares at least one parent with the other person. A male sibling is a brother, and a female sibling is a sister. Somebody with no siblings is an only child. While some circumstances can cause siblings to be raised separately (such as foster care), most societies have siblings grow up together. This causes the development of strong emotional bonds, with siblinghood considered a unique type of relationship. The emotional bond between siblings is often complicated and is influenced by factors such as parental treatment, birth order, personality, and personal experiences outside the family. Medically, a full sibling is a first degree relative and a half sibling is a second degree relative as they are related by 50% and 25%, respectively.

The word sibling was reintroduced in 1903 in an article in Biometrika, as a translation for the German Geschwister, having not been used since Middle English, specifically 1425. Siblings or full siblings ([full] sisters or brothers) share the same biological parents. Full siblings are also the most common type of siblings. Twins are siblings that are born from the same pregnancy. Often, twins with a close relationship will develop a twin language from infanthood, a language only shared and understood between the two. Studies corroborate that identical twins appear to display more twin talk than fraternal twins. At about 3, twin talk usually ends. Twins generally share a greater bond due to growing up together and being the same age. Half siblings (half sisters or half brothers) are people who share one parent. They may share the same mother but different fathers (in which case they are known as uterine siblings or maternal half siblings), or they may have the same father but different mothers (in which case, they are known as agnate siblings or paternal half siblings. In law, the term consanguine is used in place of agnate). In law (and especially inheritance law), half siblings have often been accorded treatment unequal to that of full siblings. Old English common law at one time incorporated inequalities into the laws of intestate succession, with half siblings taking only half as much property of their intestate siblings' estates as siblings of full blood. Unequal treatment of this type has been wholly abolished in England, but still exists in Florida. Three quarter siblings share one parent, while the unshared parents are siblings to each other, for example, if a man has children with two women who are sisters, or a woman has children with a man and his son. In the first case, the children are half siblings as well as first cousins; in the second, the children are half siblings as well as an avuncular pair. They’re genetically closer than half siblings but less genetically close than full siblings, a degree of genetic relationship that is rare in humans and little studied. Diblings, a portmanteau of donor sibling, or donor conceived sibling, or donor sperm sibling, are biologically connected through donated eggs or sperm. Diblings are biologically siblings though not legally for the purposes of family rights and inheritance. The anonymity of donation is seen to add complication to the process of courtship.

Consanguinity is the measure of how closely people are related. Genetic relatedness measures how many genes a person shares. As all humans share over 99% of the same genes, consanguinity only matters for the small fraction of genes which vary between different people. Inheritance of genes has a random element to it, Consanguinity decreases by half for every generation of reproductive separation through their most recent common ancestor. Siblings are 50% related by consanguinity as they are separated from each other by two generation (sibling to parent to sibling), and they share two parents as common ancestors
A fraternal twin is a sibling and, therefore, is related by 50% consanguinity. Fraternal twins are no more genetically similar than regular siblings. As identical twins come from the same zygote, their most recent common ancestor is each other. They’re genetically identical and 100% consanguineous as they’re separated by zero generations
Half siblings are 25% related by consanguinity as they share one parent and separated from each other by two generations
A person may share more than the standard consanguinity with their sibling if their parents are related (the coefficient of inbreeding is greater than zero). Interestingly, half siblings can be related by as "three quarters siblings" (related by 3/8) if their unshared parents have a consanguinity of 50%. This means the unshared parents are either siblings, making the half siblings cousins, or parent and child, making them half aunt uncle and niece nephew.

In practice, full siblings do not share exactly 50% of their DNA, as chromosomal crossover only occurs a limited number of times and, therefore, large chunks of a chromosome are shared or not shared at one time. In fact, the mean DNA fraction shared is 50.28% with a standard deviation of 3.68%, meaning approximately 1/4 of sibling pairs share more than 52.76% of their DNA, while 1/4 share less than 47.8%. There is a very small chance that two half siblings might not share any genes if they didn't inherit any of the same chromosomes from their shared parent. This is possible for full siblings as well, though even more unlikely. But because of how homologous chromosomes swap genes (due to chromosomal crossover during meiosis) during the development of an egg or sperm cell, however, the odds of this ever actually occurring are practically non existent.

The theorizing and study of birth order can be traced back to Francis Galton's (1822–1911) theory of birth order and eminence and Alfred Adler's (1870–1937) theory of birth order and personality characteristics.

In his book English Men of Science: Their Nature and Nurture (1874), Galton noted that prominent composers and scientists are over represented as first borns. He theorized three main reasons as to why first borns are generally more eminent:
Primogeniture laws: first borns have access to their parents' financial resources to continue their education. Middle Children: Feel like outcasts of families as they lack primacy of the first child and the "attention garnering recency" of the youngest. These children often go to great lengths to de identify themselves with their siblings, in an attempt to make a different and individualized identity for themselves as they feel like they were "squeezed out" of their families.

Today, the flaws and inconsistencies in birth order research eliminate its validity. It is very difficult to control solely for factors related to birth order, and therefore most studies produce ambiguous results. The social interaction that occurs as a result of birth order however is the most notable. Older siblings often become role models of behaviour, and younger siblings become learners and supervisees. Older siblings are at a developmental advantage both cognitively and socially. The role of birth order also depends greatly and varies greatly on family context. Family size, sibling identification, age gap, modeling, parenting techniques, gender, class, race, and temperament are all confounding variables that can influence behaviour and therefore perceived behaviour of specific birth categories. The research on birth order does have stronger correlations, however, in areas such as intelligence and physical features, but are likely caused by other factors other than the actual position of birth. Some research has found that firstborn children have slightly higher IQs on average than later born children. However, other research finds no such effect. It has been found that first borns score three points higher compared to second borns and that children born earlier in a family are on average, taller and weigh more than those born later. Literature reviews that have examined many studies and attempted to control for confounding variables tend to find minimal effects for birth order on personality. In her review of the scientific literature, Judith Rich Harris suggests that birth order effects may exist within the context of the family of origin, but that they are not enduring aspects of personality. In practice, systematic birth order research is a challenge because it is difficult to control for all of the variables that are statistically related to birth order. For example, large families are generally lower in socioeconomic status than small families, so third born children are more likely than first born children to come from poorer families. Spacing of children, parenting style, and gender are additional variables to consider.

Regressive behaviors are the child's way of demanding the parents' love and attention. The arrival of a new baby is especially stressful for firstborns and for siblings between 3 and 5 years old. In such situations, regressive behavior may be accompanied by aggressive behavior, such as handling the baby roughly. All of these symptoms are considered to be typical and developmentally appropriate for children between the ages of 3 and 5. While some can be prevented, the remainder can be improved within a few months. Regressive behavior may include demand for a bottle, thumb sucking, requests to wear diapers (even if toilet trained), or requests to carry a security blanket. The American Academy of Pediatrics suggests that instead of protesting or telling children to act their age, parents should simply grant their requests without becoming upset. The affected children will soon return to their normal routine when they realize that they now have just as important a place in the family as the new sibling. Most of the behaviors can be improved within a few months. The University of Michigan Health System advises that most occurrences of regressive behavior are mild and to be expected; however, it recommends parents to contact a pediatrician or child psychologist if the older child tries to hurt the baby, if regressive behavior does not improve within 2 or 3 months, or if the parents have other questions or concerns.

"Sibling rivalry" is a type of competition or animosity among brothers and sisters. It appears to be particularly intense when children are very close in age or of the same gender. Sibling rivalry can involve aggression; however, it is not the same as sibling abuse where one child victimizes another. Sibling rivalry usually starts right after, or before, the arrival of the second child. While siblings will still love each other, it is not uncommon for them to bicker and be malicious to each other. Children are sensitive from the age of 1 year to differences in parental treatment and by 3 years they have a sophisticated grasp of family rules and can evaluate themselves in relation to their siblings. One study found that the age group 10–15 reported the highest level of competition between siblings. Sibling rivalry can continue into adulthood and sibling relationships can change dramatically over the years. Approximately one third of adults describe their relationship with siblings as rivalrous or distant. However, rivalry often lessens over time and at least 80% of siblings over age 60 enjoy close ties. Evolutionary psychologists explain sibling rivalry in terms of parental investment and kin selection: a parent is inclined to spread resources equally among all children in the family, but a child wants most of the resources for him or herself. Jealousy occurs in a social triangle of relationships which do not require a third person. The social triangle involves the relationships between the jealous individual and the parent, the relationship between the parent and the rival, and the relationship between jealous individual and the rival. These implicit beliefs determine both the intensity of their jealous feelings, and how long those jealous feelings last. The first category is conflict about equality or fairness. It is not uncommon to see siblings who think that their sibling is favored by their teachers, peers, or especially their parents. In fact it is not uncommon to see siblings who both think that their parents favor the other sibling. Perceived inequalities in the division of resources such as who got a larger dessert also fall into this category of conflict. This form of conflict seems to be more prevalent in the younger sibling.

The saying that people "fight like siblings" shows just how charged sibling conflict can be and how well recognized sibling squabbles are. In spite of how widely acknowledged these squabbles can be, sibling conflict can have several impacts on the sibling pair. It has been shown that increased levels of sibling conflict are related to higher levels of anxiety and depression in siblings, along with lower levels of self worth and lower levels of academic competence. In addition, sibling warmth is not a protective factor for the negative effects of anxiety, depression, lack of self worth and lower levels of academic competence. This means that sibling warmth does not counteract these negative effects. A study on what the topic of the fight was (invasion of personal domain or inequality) also shows that the topic of the fight may have a result on the effects of the conflict. This study showed that sibling conflict over personal domain were related to lower levels of self esteem, and sibling conflict over perceived inequalities seem to be more related to depressive symptoms. However, the study also showed that greater depressive and anxious symptoms were also related to more frequent sibling conflict and more intense sibling conflict. Techniques in which parents encourage physical aggression between siblings may be chosen by the parents to help children deal with aggression in the future, however, this technique does not appear to be effective as it is linked to greater conflict levels between children. Parental non intervention is also linked to higher levels of sibling conflict, and lower levels of sibling warmth. It appears that child centered parental interventions have the best effect on sibling's relationship with a link to greater levels of sibling warmth and lower levels of sibling conflict.

Studies on social skill and personality differences between only children and children with siblings suggest that overall the presence of a sibling does not have any effect on the child as an adult.

There have always been some differences between siblings, especially different sex siblings. Often, different sex sibling may consider things to be unfair because their brother or sister is allowed to do certain things because of their gender, while they get to do something less fun or just different. McHale and her colleague conducted a longitudinal study using middle childhood aged children and observed the way in which the parents contributed to stereotypical attitudes in their kids. In their study the experimenters analysed two different types of families, one with the same sex siblings, and the other with different sex siblings, as well as the children's birth order.

Anthropologist Edvard Westermarck found that children who are brought up together as siblings are desensitized to sexual attraction to one another later in life. This is known as the Westermarck Effect. It can be seen in biological and adoptive families, but also in other situations where children are brought up in close contact, such as the Israeli kibbutz system and the Chinese shim pua marriage.