I hung out with cousins sometimes as a kid and honestly am glad I don't have to anymore as an adult. It was always awkward and uncomfortable feeling. There was just no reason I wanted to be around them and ultimately I still had to be because they were _family_ as if that actually matters.
My wife and I are each one of three kids, and we have two kids ourselves. She wanted a third because she very much wanted our kids to have the same experience of having two siblings. The thing is, our kids have no experience of having two siblings -- having only one is all they know, and they're very close.
Maybe my kids will themselves want a family, or maybe they won't. I have no nieces or nephews on my side but do on my wife's side. At least as far as this subject goes, I don't ruminate on what might have been. Que sera, sera.