I could have started young, but....
Reading the Solo stories I am impressed as to how young so many people start with sex, and also how often it is the girls that first initiate the activity.
When I was only about 5 years old I was at the seashore at my grandparents house, the house was built on pilings and you could go underneath and walk around (for a 5 year old that is). One day I saw two girls go in there, one was chubby and about 11 years old, maybe, the other was younger, about 7 or 8. Curious as to what they were doing, I went in and looked around. The girls had their dresses pulled up and panties off, the younger one was on top of the other and moving around. When they say me, they quickly stopped what they were doing and the older girl said,
'We were trying to fuck, but two girls can't do it, we need a boy to do it. Would you fuck us?'
I had some idea what they wanted me to do and began going towards them. But then the younger one began to object,
'No, no, he is so young, we might get in trouble.'
They got their clothing back in order and left the crawl space.
I have often wondered if my life would have been different if there had been no objections by the girl, I would have had my first sex at 5 and would have become experienced beyond my years, and probably continued with a very sexually active summer as my parents were not there and my grand parents did not keep very good track of my activities. And certainly would have had a different attitude towards sex and girls than the way I grew up, being shy and afraid of approaching them for many years.