My clan has shrank considerably now, from 60+ to only 22, still no kids popping up, got two young couples with no kids and no pregnancies after years, definitely seems bugged.
Awesome will do
I've created 5 different kingdoms, I've tried everything man the clan that takes leadership of the kingdom will copy your banner.
Don't be a part of a faction, capture a settlement, install a governor and then talk to them and you'll have the dialogue option to declare a new kingdom