Kinship is a psychological construct of some sort of familiar tie. We see this in the crime world, for example. Trust allows us to engage in trade, right? It's hard to imagine trade in the sence of trust. And if you and i were drug dealers and i wanted you to manage my books, if you stole from me, i couldn't sue you. I can't bring you to court because we're drug dealers. So how do i overcome trustee, the trust hurdle? Well, if you were a cousin of mine, i might actually let you manage my books as you're less likely to defect on me. That's teething problems with kinships.