Sibling
The word sibling was reintroduced in 1903 in an article published by the journal Biometrika. This specific term had not been used since Middle English, specifically around the year 1425. Before this revival, people simply called a male sibling a brother and a female sibling a sister. A person with no siblings is known as an only child. Full-siblings share the same biological parents and are considered first-degree relatives. Half-siblings share one parent and are classified as second-degree relatives. The medical definition states that full-siblings are related by 50% while half-siblings are related by 25%. Three-quarter siblings exist when unshared parents are first-degree relatives to each other. Diblings are biologically connected through donated eggs or sperm but lack legal family rights. Stepsiblings are children of one's stepparent from a previous relationship. Adoptive siblings are raised by a person who is the adoptive parent of one and the biological parent of the other.
In practice, full siblings do not share exactly 50% of their DNA due to chromosomal crossover. Studies show the mean DNA fraction shared is 50.28% with a standard deviation of 3.68%. Approximately one quarter of sibling pairs share more than 52.76% of their DNA. Another quarter shares less than 47.8%. Identical twins come from the same zygote and are genetically identical at 100% consanguineous. Fraternal twins are no more genetically similar than regular siblings. Half-siblings can be related by three-quarters if their unshared parents have a consanguinity of 50%. This means the unshared parents are either siblings or parent and child. There is a very small chance that two half-siblings might not share any genes if they did not inherit any of the same chromosomes from their shared parent. However, homologous chromosomes swap genes during meiosis making this practically non-existent. Twin studies examine how often identical twins possess the same behavioral trait compared to fraternal twins.
Francis Galton published English Men of Science: Their Nature and Nurture in 1874 noting prominent scientists were over-represented as first-borns. Alfred Adler developed theories on birth order and personality characteristics between 1870 and 1937. Firstborns fulfill family roles of leadership and authority while seeking out order and structure. Middle children feel like outcasts of families as they lack primacy of the first child. Youngest children feel disadvantaged compared to older siblings and are often perceived as less capable. Frank Sulloway published Born To Rebel in 1996 arguing firstborns are more conscientious and socially dominant. Judith Rich Harris suggested birth order effects may exist within the context of the family of origin but are not enduring aspects of personality. Resource dilution models suggest parental resources are finite and first-born children get full access. Confluence models propose intellectual environments change due to three factors affecting first-born advancement. Systematic research is a challenge because large families generally have lower socioeconomic status than small families. Some research found firstborn children score three points higher on IQ tests compared to second borns.
Regressive behaviors occur when a new baby arrives especially for firstborns and siblings between 3 and 5 years old. The American Academy of Pediatrics suggests parents should grant requests without becoming upset. Regressive behavior may include demand for a bottle, thumb sucking, or requests to wear diapers. The University of Michigan Health System advises contacting a pediatrician if regressive behavior does not improve within 2 or 3 months. Sibling rivalry appears particularly intense when children are very close in age or of the same gender. One study found that the age group 10, 15 reported the highest level of competition between siblings. Approximately one-third of adults describe their relationship with siblings as rivalrous or distant. At least 80% of siblings over age 60 enjoy close ties. Jealousy occurs in a social triangle involving relationships between the jealous individual, parent, and rival. Four classes of children were identified based on different responses of jealousy to new infant siblings. Regulated Exploration Children make up 60% of children while Disruptive Children account for 2.7%. Older children tend to be less jealous than their younger sibling due to better mental processing abilities.
Studies on social skill differences suggest overall the presence of a sibling does not have any effect on the child as an adult. Working-class families benefit culturally from increased time those siblings spend together. Higher sibling warmth is related to better social skill and higher perceived social competence. Increased levels of sibling conflict are related to higher levels of anxiety and depression in siblings. Sibling conflict is also linked to an increase in more risky behavior including smoking cigarettes and skipping days of school. A study showed sibling conflict over personal domain was related to lower levels of self-esteem. Sibling conflict over perceived inequalities seems to be more related to depressive symptoms. Parental non-intervention is linked to higher levels of sibling conflict and lower levels of sibling warmth. Child-centered parental interventions have the best effect with links to greater levels of sibling warmth. Gender roles among children vary depending on whether parents hold traditional values or not. In homes where fathers held traditional values, kids played gender-based roles in the home.
Anthropologist Edvard Westermarck found that children brought up together as siblings are desensitized to sexual attraction later in life. This phenomenon is known as the Westermarck Effect. It can be seen in biological and adoptive families but also in situations like the Israeli kibbutz system. The Chinese shim-pua marriage also demonstrates this effect. Milk kinship exists in cultures with milk kinship and in Islamic law. Cross-siblings are individuals who share one or more half-siblings. God siblings are the children of the godfather or godmother. Stepsiblings are children of one's stepparent from a previous relationship. Siblings-in-law are the siblings of one's spouse. Co-siblings may refer to the spouse of one's spouse's sibling. These relationships exist across different family structures globally. Cultural concepts shape how siblinghood is understood beyond blood relations alone.
Common questions
When was the word sibling reintroduced into English usage?
The word sibling was reintroduced in 1903 in an article published by the journal Biometrika. This specific term had not been used since Middle English, specifically around the year 1425.
What percentage of DNA do full siblings share according to medical definitions and studies?
The medical definition states that full-siblings are related by 50% while half-siblings are related by 25%. Studies show the mean DNA fraction shared is 50.28% with a standard deviation of 3.68% due to chromosomal crossover.
Who published Born To Rebel and what argument did they make about firstborns?
Frank Sulloway published Born To Rebel in 1996 arguing firstborns are more conscientious and socially dominant. Firstborns fulfill family roles of leadership and authority while seeking out order and structure.
How does regressive behavior manifest when a new baby arrives for siblings between 3 and 5 years old?
Regressive behavior may include demand for a bottle, thumb sucking, or requests to wear diapers. The University of Michigan Health System advises contacting a pediatrician if regressive behavior does not improve within 2 or 3 months.
What phenomenon explains why children brought up together as siblings are desensitized to sexual attraction later in life?
Anthropologist Edvard Westermarck found that children brought up together as siblings are desensitized to sexual attraction later in life. This phenomenon is known as the Westermarck Effect and can be seen in biological and adoptive families but also in situations like the Israeli kibbutz system.