If the kids are old enough for sex, they must be old enough to take care of a baby and provide for it without grandma and granpa around.
Let us say 18.
And anyone over 18 having sex with a minor should be permanently removed from society. Maturity means patience and good judgement.
The “ability” to procreate doesn’t mean you have to, just like the ABILITY to stab someone doesn’t mean its okay to go out and stab people.
So you jail the 18 yo woman with the 17 yo boyfriend?
Lots of our parents would still be in prison under your idea. Our grandparents would have been hung.
Sure you want to go there?
Look, this is pointless. Believe whatever you like. History, the very history that created/resulted in both our existence does not care what either one of us think.
But if you want 30 yo bubblewrapped children, keep on your present line of thought. Because it’s exactly how we got to 26yo bubble wrapped children. And 21. and 18....