I found another thread that lists some events that might come and save my tribe. Whew! So all is not auomatically lost, even if the last nursing child is also a boy.

The woman who doesn't have kids is 32. Plenty of time to keep trying with her, but since she hasn't gotten pregnant in 14 years, I'm thinking it's pretty hopeless. But I've set her and a couple men to prefer "Parenting", so maybe I'll check on them one morning and be surprised.

Thanks for the encouragement.