How old do they have to be to breed? It keeps saying they are too young for that? also, if i have breeding selected, will they do that on their own, or will I have to keep making them?

Villagers need to be 18 years old to breed. The 14-17 year olds look grown, but they simply aren't mature enough for all that responsibility!

Once a villager has some skill in breeding, you'll have trouble controlling them! One experienced male can keep an entire female population sitting in village center all the time! You might want to keep that in mind as you plan your strategy for the game.

What I've been doing with my breeders, is I'll make one female a breeder, and that way it somewhat limits the amount of growth. I also like to alternate their breeding skill with another one to give them something to do between babies (helps them fight that "urge").
Has anyone else realized that women can breed into their 70s? Apparently menopause doesn't affect villagers

Yes, it's true that villagers can breed until they die. But, it can be "risky" to breed the elderly women - if a mother dies while she's nursing a baby, the child will die with her.