Yes. But if you're suggesting that you could treat differences with cousins as random, the way we can treat differences with siblings, then no, because of assor

Yes. But if you're suggesting that you could treat differences with cousins as random, the way we can treat differences with siblings, then no, because of assortative mating; e.g. if my cousin's "good genes" came from my uncle, then maybe he married my very rich aunt who left my cousin a large inheritance.