When I was 5 or so my sister dressed me in her communion dress for a laugh, hated it simply because of sibling rivalry but I recall my mom putting lipstick on me as a joke which I remember finding fun but I wouldn't relate it to crossdressing.
I was at my god mothers one time and she asked would I tidy up her kids playroom for 5 pounds(dollars) which I did and found a blonde wig which I wore doing it, I remember being afraid her or my mom would catch me doing it.
Around 6 or 7 I had a female friend who was my best friend since we lived in an area with a lot of older families with few young children and I remember she gave me a make over one time which I enjoyed but had no idea why, years later she had moved away and I stayed the weekend once and she did ballet and thought it'd be fun to let me try on her ballet clothes which then I knew I'd enjoy doing.
As a young teen my mother got married and I got a step brother and sister slightly younger then me and she'd often dress the two of us up which I definitely liked doing and my step brother didn't.
My first girlfriend was my step sisters friend and I told her about my dressing because I had learned what crossdressing was and wanted to do it, she bought me a corset and a mini skirt for 1 of my birthdays as well as gave me some of her old clothes. She seemed supportive but I never really dressed in front of her more then once or twice.
A funny story was we were making out on her couch one time and she put lip gloss on me, later she went into her kitchen and her sisters boyfriend asked her was she painting her face with lipgloss because she had it all over her cheeks and forehead and that I was hardly wearing lipgloss. We had a good laugh over that.
