Actually, you're right about that, Jules. Some guys are pretty much 50/50, but many of them actually produce more of one than the other. Genetics will generally tell you which one your guy probably leans toward (if he has all sisters then you're likely to get girls or vice versa if he has all brothers). My DF is probably about 50/50 though as he technically has three sisters (he only keeps in touch with one as the other two were from his father's previous marriage and they don't keep in contact with him) and two angel brothers (2nd trimester stillbirths). Women are actually also more receptive of one type of sperm or the other depending on their diet, which is why experts say that diet is the most important factor in gender swaying.