Okay, a tad more serious and related question:
What if they didn't know this about themselves? It happens sometimes when a child is born with birth defects or other chromosomal issues that lead to ambiguity. The parents then usually have to make a decision about which to assign the child, and they can get it wrong (there are even documented cases of this happening*). The child only finds out later, sometimes at puberty, or even later. And if in the unfortunate circumstance that they were left orphaned before being told about it, it's not totally inconceivable that they might not find out until they're well into a serious relationship. What then?
*and of overbearing, abusive doctors that took it upon themselves to do something without the parents' consent, or of botched surgery that lead to similarly 'wrong' assignment under coercion, or so on.