Yep. And sibling relationships become even more of allying because instead of inheritance being a competition, inheritance can work for all of them if they all play it right.

But you know what? Maybe Barrayar's Barrayar. But it's Beta Colony that does line marriages, what with their economic tests to be able to have kids; marriages will accumulate resources as more people join, therefore, more ability to have kids. And then Cordelia shows up on Barrayar and wonders where the hell the rest of everyone's marriage is.