He found that only the number of biological elder brothers had an impact on a later-born boy's sexual orientation; non-biological siblings had no effect.
He found that only the number of biological elder brothers had an impact on a later-born boy's sexual orientation; non-biological siblings had no effect.
他发现，仅亲哥哥的数量对后出生男孩的性取向有影响，而非亲兄弟则没有。