Bogaert found that the link between having older brothers and homo was present only if the siblings were biologically related - this was seen between biological brothers who were not raised together 博格特发现，只有弟弟和哥哥之间有血缘关系时，弟弟才会受影响成为同性恋，即使是他们不一起长大，这种影响也存在。
