I guess that I always assumed that it was hereditary. I found out recently that the 7 year old son of one of my friends has a "freakishly big cock" by her description. She said that he was really big even when he was born and that he now has a flaccid penis every bit as big as his 16 year old brother.

When someone else quizzed her a bit, she said the doctor thought it might it might have been a burst of hormones in the womb or something like that. She even let on that the boy's father was actually pretty small, despite a huge frame. Another friend, who already knew about the boy and assumed the father must have been big too, said "wow, that sucks for (the father)." The mother actually added, "it screws with his older brother more. How would you like to be 16 and hung smaller than you 7 seven old brother?"

Given the importance of the sex hormones in the development of the fetus, I am guessing there are some genetic predispositions and some that happen out of somewhat random events during preganancy.