I have responded in the past to several similar threads. The earliest I found was from September 7, 2006, started by "Tiana" and entitled "How old were you when the urge began?". My reply then was as follows:
Late developer!
Clearly I'm in the minority having, as far as I remember, not tried on any female clothes until I was 13 (late 1950s). I had no sisters and, like most of my male contemporaries in the area wher I lived, went to an all-male secondary school. My only "contact" with girls was when travelling to and from school. My interest in the opposite sex was great - because I had had so little close experience with girls. I noticed that the girls started wearing stockings when they reached about 12 or 13 and I was fascinated to know what it felt like.
My grandmother, who lived with us, died in 1957 and that meant I was alone in the house when I returned from school. I decided to find a pair of my mother's stockings and try them on. Of course, they wouldn't stay up. I tried elastic bands to keep them up but that was unsatisfactory. I knew about girdles and corsets but didn't know whether that's what the girls I watched used to hold up their nylons. I found an old (pink-coloured Gossard) girdle at the bottom of a drawer (probably no longer worn by my mother) and tried that. It was too loose and I had to put a leather trouser belt on to secure the girdle round my waist.....but then, for the first time, I could get some idea what girls felt like wearing stockings. I also found a grey, pleated skirt in my mother's wardrobe and put that on as well. It was quite long, well below my knees, but was the nearest I could get to the school outfits that I saw the girls around me wearing. From that time, opn two afternoons a week when school finished early and I had the house to myself, I would dress up - though with a very limited "wardrobe"!