This is a post dedicated to the causes of this phenomenon called the "fa'afafine." The birth order has been a very interesting topic when taking into consideration the possible outcomes of having a fa'afafine in the family. First, the fa'afafine is generally decided by the parent's of the children... Or is it? Usually Samoans have many children in their respective families. Gynephilia refers to males that have a sexual attraction to adult females. On the other end of the spectrum is androphilia, which is the sexual attraction to adult males.
Now scientific studies show that we "compare the birth order of androphilic males (i.e. fa'afafine) and gynephilic males from the politically autonomous Polynesian nation of Independent Samoa. Results indicate that relative to gynephilic males, fa'afafine tend to have more siblings and are generally later born when birth order is quantified using Slater, fraternal and sororal indices. More specifically, fa'afafine tend to have a greater number of older brothers, older sisters and younger brothers" (The Royal Society 2007). That is kind of a very broad statement, but it basically states that usually the later born males in these Samoan families are genetically programmed to be androphilic which means they prefer men, which would be easier for them to assume the female role as the "fa'afafine."