I started just before my teenage years. Had a sister and two stepsisters who always seemed to get away with everything while I always seemed to get the short end of the stick. Complaining to them about it got nowhere, they always said "You don't know what it's like to be a girl!" and never argued anything further.
One night, I went to my mom and asked what it was like to be a girl. Her response was that it was just something you do. After a bit, she suggested for me to dress up to get an idea of what it was like and she put me in one of her dresses. I was told that with a little makeup and my hair done, I'd be a very pretty girl. I wanted to see, so next day we did that. That was the point mom said that I looked good enough dressed that maybe she should start getting me dresses and skirts. Was a bit taken aback, but she offered to buy me things if I would wear them. I kind of liked it, so I agreed to it.
That started several years of very regular dressing, both at home and outside. I left it behind when I went to college, but the memories are always there.