My uncle once went to his brother's daughter's wedding and there discovered that the groom's cousin was his extranged son's ex-wife, and that is how he got to finally meet his grandkids. (But that's mostly because they were all still in the same town.)

But yeah, it's interesting in the context of communities that are large but disperse! The simple example is with communities that are just very low population density but iirc what they've found with Aboriginal groups in Australia is that, contrary to expectation, the moiety system actually spread further after the colonization, because the aboriginal communities got even more fractured and that shortcut to kinship became even more important than before.

I am so in favor of all relationship structures that maximize the number of people on call to help with the babies! I think I would be delighted to be a parent but only once the parent-to-baby ratio was 4:1 or higher.