Every since upgrading to an XS max over the weekend, I have had issues with iMessages from my family merging into the same thread. No matter if I get a text from my wife or my kids, it all comes up in the same thread even though it's a 1 on 1 conversation. Even if I try to start a brand new message thread, no matter which name (of the three in my family) I type in, it reverts back to the previous thread. The only fix so far is to delete that thread, but eventually the issue arises again. I was on the phone with Apple support for over 4 hours this weekend and they couldn't figure it out either. They are telling me that the issue arose because we were all under the same Apple ID (even though we never had this issue before this weekend). So I gave everyone in my house a different Apple ID and put them all under my iCloud account. Hoping someone in the forum has seen this issue because it certainly has Apple support stumped.