Sorry to hear this happened to your family. Hopefully you'll start a brand new family and use the tips posted on this page. You just need to be persistent. Do you know how to delete just that family to start a new one?

It also helps to pause the game and make a backup copy of that game slot before your adults get too old to have children. That way if something happens to those adults, you can use your backup rather than having to start the game all over from the beginning.