It seems to me that having girls around may have made dressing easier but probably wasn't a factor in why we start doing it.
Millisense: I started having weird feelings about things when I was probably in the second grade, so around 7. My mom had a spare bedroom and I found a drawer that she kept frilly things in, lots of lacy poofy things. Nothing fit but I played with the stuff a bit. I remember playing with her makeup and getting in trouble for it. I'm sure if I'd had access to girl clothes that fit me I would have worn them. I didn't actually do a full scale cross dressing experiment until about 4 years ago, had no clue what I was doing with the makeup and looked like a nut and felt really ashamed about it.
