I don’t have a larger answer, but combining personal yet mundane relationships (brother-in-law, foster child, etc) with more “spicy” variants (love triangle, etc.) seems like a generally great approach to generating interesting relationship maps. A lot of games try to make them all “interesting”, I think, which dilutes the awesome. Having those more “normal” relationships we can relate to mixed in with the more interesting stuff, I would expect, can generate a lot more exciting play. “I want to kill him… but he’s married to my sister” is much more interesting than just having a death grudge against someone.