Speaking as a father I will kill any older person messing around with my kid. I'll beat the hell out of any young person messing with my kid. OK protective father mode off.
It was not that many decades ago that if a girl was not married by 16 she was an old maid. Sadly sexually most girls today are more mature and active w/o marriage, while to immature to take care of themselves much less a house. It is hard to say when a child is an adult, even many laws have what if's attached.
Now if I were single I would not look for anyone under 18. But if I cannot say I would not date a 20 year old, of course any 20 year old that would want an old fart like me would probably be looking forward to cashing life insurance checks. Dust be careful.
So my answer who knows just stay away from my kids. :evil: