Well, admission alert...I did too when I was really little. In addition to all the boy stuff tho.
I'm wary of the "never would have been normal" line because it's not clear that what you are seeing in your friends is nurture not nature. It sounds like they have had rough lives, and it is possible that a traumatic incident in childhood (such as an abusive male figure in the house) can disrupt a child's normal development.
I'm curious why there is no rabid search for the "gene" that leads to bulimia, or social phobia, etc. etc.
Other than the youngest, and ironically the most normal, they didn't have trauma...they had a lot of money, a businesman father who was fairly passive around the house, a stay at home doting mom...The Waltons...or so we thought. On the other hand, I know a number of people who had abusive childhoods who are very straight. So...maybe only God knows the answer for sure.