Nah, if I reconsidered at 50 I already outlined what I'd do: join Big Brothers. There are a lot of ways one can nurture and excercise the paternal instinct without having children. If someone's reason for having kids is truly based on love and a desire to share and nurture whose genes make the kids won't matter to them.
Because they (the "parents") are too freakin' lazy to bring their spawn up properly. A little careful work at age 2 can make age 16 tremendously easier. Two year olds intensely dislike the word "no". Wise mothers and fathers use it anyway, and make it stick. Foolish mothers and fathers allow whining, wheedling, and crying to convert "no" to "maybe", and finally to the fateful "yes, but just this one time". The snotty nosed little brats you see running amok in public are usually the spawn of selfish, lazy, morons. Such behaviour is not inevitable.
OBTW, my whiny, immature, compalining coworkers were definitely self-starters on the subject of the general, inevitable horridness of children.
AB
Actually, if you "reconsider" at 50, you might want to consider adoption at that point. There are many children in this world for whom a 50 year old parent is a a thousand times better than no parent at all. :)