Random helpful tips about Adultery and Eugenics.

[Kiethoo]

Recently started a new game (♥♥♥♥♥♥♥ onedrive !) after all my saves were lost,
Im at the point now where my family are genetically superior superhumans. So now I want to start spreading the Eugenics around to my vassals.

I was going to marry off my Cousin to one of my vassals.
Said Vassal is...

1 Intrigue skill.
Trusting
Chaste
Craven
also Homosexual ( though If I recall in ck3 this doesn't effect fertility rates, that was Ck2? )

Once my character has helped my cousin produce several kids I can interbreed them with the children my wife has had to stabilize a crop of future children and give them titles.

Then next generation repeat with a new vassal of a different dynesty.

Anything I might be forgetting?
Any tips that might smooth things out?

I don't plan on making incest part of my religion as it's generally not part of Luthers and im playing as Saxon Germania.