Outside of your immediate family, the people you are related to barely qualify as acquaintances in both a genetic and a general interest sort of way. Second cousins? Great-uncles? Who the fuck are these people? Them and a sasquatch will get you a sequel to Willow Creek. Was that even a joke? It is to your second cousin.
At some point, you have to prune your family tree and accept that it's too big and that the extras are just a nuisance, and that's if you're being kind. Trace your roots far enough and you're probably related to half the country in some watered-down, unimportant way, so the bonds of "blood" don't necessarily mean a lot beyond the potential to get a new kidney should you ever damage yours in an unlicensed back-alley boxing match.
We have a routine of inviting family for the holidays that has kept us going as a species for generations now. Thanksgiving is about family because something something 25-pound turkey something pilgrims. You're not going to eat that much food on your own, and you're not going to invite any First Nations people over; that would be weird. Better invite your cousin. Cousin, eat this fuckin' log of cranberry: no one else wants it, and I don't know why I bought it. And he will, too, the son of a bitch, with his fingers. Same ones he grubbied across the Triscuits and assorted cheeses you put out before dinner because you figure that's what people do.
When you're a kid it's kind of fun to have the family over, and it grows increasingly less fun as you age until the day the torch gets passed to you to have a family dinner, and then, for some ungodly reason, you do it. You want to see what it's like, and what it's like is waking up at 6 a.m. to stuff a goddamn turkey and bake sweet potatoes and devil eggs for the next 8 hours so that 15 people can descend on your home like a swarm of gluttonous vultures, spend 30 minutes tearing everything apart, another hour digesting and farting, and then leave you with the mess to clean up. And you did it because your parents did it. Know what else your parents did? Had sex with each other. Not all their ideas are things you want to try out.