Gavelkind is not so bad if you consider that the game is about DYNASTY and not your character at the current time. Its in your family, you've got claims, you can always then switch to seniority or elective for chosing different rulers in different countries! It gives the game more fun factor, when your dynasty is big, and you switch to different duches, and not just sit for whole game in your perfectly upgraded de-jure duchy.
Unless you want to build a kingdom. Having my territories splinter off after I just finished unifying the country seems counterproductive to me. How am I going to build an Empire if I have to keep starting from square 1?
If you can afford constant, rapid expansion, its not much of a problem - just keep trashing dudes and giving land to your heirs. One cool thing about Gavelkind is the extra Desmene, so if you play your cards right you can have super-desmenes that allow you to snowball it into further conquest - just DON'T make more than two duke titles for yourself.
On the other hand, if you're stone-walled against a blob, you got a problem.
One thing a lot of dudes do, is to get an old wife with big stats and then use the Seduction Focus to breed bastards with hot bitches with nice congenital traits. When you get a son you like, legitimize him, maybe his second-best brother as well, in case you need a backup.
Well, I fucked up. I bred together 2 members of my dynasty who had the same grandfather, and now their offspring are developing inbred and imbecile traits.
Its not my main dynasty, fortunately, but its still a problem. Now I have to try to weed them out before they can continue to reproduce.
A long time ago I read that this game was about Eugenics. I can see why.
Yup, this is game has a lot of eugenics. Its all about breeding the proper Genius Strong Attractive super-men that will lead your House to greatness.
Cousins? Pfff, those barely count.
Wait until you have to manage incestual Zoroastrian/Messalian/Dawnbreaker Zunist/Reformed Incestual Pagan families.
You have to do a careful balance between incest breeding and introducing new blood through concunbines and normal royal marriages. It does help the eugenics in some regards.
Suggestion: Marry them to a rival dynasty.