I have a huge extended family and I'm the only one who doesn't go to its gatherings (weddings, funerals, Christmas). Us being related is just a coincidence. I don't feel any special bond with them (even my immediate family).
I stand a greater chance of enjoying the company of someone I "chose" (friend, spouse - even though I don't have either) as opposed to someone I'm "forced" to see or hang out with. It's like everyone goes to these gatherings just because they are supposed to and it's expected of them. Or maybe they enjoy it, I don't know.
If I met a long lost sibling I never knew existed, or a child I fathered unknowingly (not gonna happen!) or if I found out I was adopted and I'd be reunited with my birth parents, these new people in my life would just be strangers.
Do you see anything special in blood relations?