I've had my 2 male neutered cats for 6 years, adopted as an ADULT bonded pair (aged ~4 and ~6). Over the past 2 years their play has become more aggressive and they no longer snuggle together. What happened?

Their play is still play, but now with more hissing and even a little growling. Nothing beyond that. They are now ~10 and ~12. They used to snuggle in the same cat beds but now one will kick the other out to take it. They never snuggle together at all any more. They used to all the time, especially winters.

We moved to a new condo 2 years ago, that's the only difference. But within the last 6 years we've moved different apartments 3 times before the condo.

Any ideas? Would our caretaking of them have anything to do with it? Maybe one feels like the "favorite" idk.