Turns out, first-borns are more likely to learn about sex from their parents as compared to their younger siblings.
According to a new study led by the London School of Hygiene & Tropical Medicine (LSHTM), birth order may play a significant role in how children learn about sex, especially for boys. Researchers found that first-born children were more likely to report parental involvement in sex education than later-born children, a pattern which was especially pronounced in men.
The study is the first to look at the relationship between birth order and two key sexual health outcomes: parental involvement in sex education and early sexual experience.
The study's authors say that a better understanding of the relationship between birth order and parental involvement in learning about sex could help to improve the design and delivery of sex education programmes.
Dr Lotte Elton, who led the research as part of her MSc project at LSHTM, said, "Although there has been much research into how the order in which children are born into a family may impact psychological or social outcomes, studies on the relationship between birth order and sexual health outcomes are limited.
When researchers looked at sibling involvement in learning about sex, they found that all later-born children were more likely to report learning about sex from siblings compared with first-born children.
Although there is little research on how sex education from siblings might affect sexual health, associations between sibling behavior and sexual health outcomes have been documented - for example, having a sexually active brother or sister has been linked with more liberal sexual attitudes, and sisters of pregnant and childbearing adolescents have been found to be younger at first sexual intercourse.
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Given that later-born children are learning from their siblings about sex, dedicated sex education programmes could better equip adolescents to teach their younger siblings about sex, particularly where parental involvement in sex education is low.
The authors acknowledged the limitations of the study. Of particular importance is that middle-born children had different socio-demographic characteristics, including social class and ethnicity, compared to first- and last-born children, which means that even with statistical adjustment, the results for middle-born children may reflect socio-demographic differences rather than birth order.
Furthermore, although adjustment was made for sibling number, other sibling factors which were not adjusted for, such as gender and age difference, which may have been relevant.
The full findings are present in the journal- Sex Education.