I can confirm this. My kids are 20 now and I can't find them. The game says they are "holding" in my town but they have never been in the keep or somewhere else. Also, they have points for skills/perks but I can't assign them.
I agree that it makes no sense to play any longer if I can't continue with my clan and other clans die out. I aimed for a long term campaign to test and experience all the long term features for the first time (I started all over again and again, game seemed kinda stable now)...but it still makes no sense.