If the updates are too far apart, then I sometimes go through the game again sped up, just lose interest or wait for a few more updates for that game then replay the whole thing from scratch.
I'd say ideally they look similar as in real life siblings look similar.
That being said with graphics and rendering I think it's a lot harder to portrait that same siblings similarities as in real life.
I'd take the game being good and siblings not looking super similar than just a copy paste...
Japanese games that are censored and those types, I just don't even bother trying.
Sad cause some look like they have potential, but the censored I can't get past.