I'd like a small kingdom I'll rule fairly, easily defended with a competent loyal guard, lots of lovely fair maidens, abundant resources tended to by devoted farmers, and a generous amount of gold in the vault.
Best age implies maturity/experience/skill and in those categories there is a big difference as women typically mature faster than men, I'd say at best girls could start as early as 16 but I wouldn't recommend it until 18 just for wisdom's sake, but I get the youthful lust thing. Boys... maybe 17-18 but really it's better if they wait until 21+ because a boys dick rules his brain in his teens (and some beyond that) so it's a better idea to hold off the fun and frolic until they know what a monumental screw up they could possibly get into by knocking up a chick.
Ideally, i think marriage would be great, but that aint happening.
16 i think is a decent age across the board.
Granted you still have to worry about getting taken advantage of abd stuff, but realistically thats true no matter the age.
Where on your body would you get a tattoo that no one would ever see unless you showed them?
__________________ "Happiness is a lie. Life is horror. The light is always dying all across the universe. The last star will flicker out someday, when it does, all that remains is shadow. And I will be its king!"'-Amahl Farouk