I only have two cousins (yes small family), they are very nice. But we aren’t extremely close. Just civil.

My husband on the other hand has a ton of them and one is totally nasty. We only see him at family get togethers, which aren’t frequent. Otherwise we never speak to him. My husband is a bit of an outcast in his extended family. Whatever. We don’t lose sleep over it. If you need to see these people at gatherings then just be polite but you don’t need to keep friendship with them at all. Keep it to a minimum