Family Tree tips?

I’m currently working on some world building for some novellas I want to write centred around a “family saga”

It’s about a Bavarian family and starts in 1812, it will involve descendants of the original protagonist emigrating, marrying other cultures and having descendants of their own in various corners of the world.

Research is in hand and progressing

But what I want to ask is does anyone have any tips, dos or donts for filling out a realistic yet fictional family tree?

I think I’ve got it handled but I’d love a sanity check and to perhaps see some things I haven’t thought of.

Thanks for reading!