all of my original builders have died and for some reason none of my children will learn the skill. is there something i need to do special or should i just wait and hope for someone to become a builder?

A villager won't learn a new skill without your help. You need to teach some of your villagers the construction trade, so that you can have some builders. If you have no other building projects available, drop them on one of the huts that they built, and they can learn by fixing huts.