i message weirdness

Two of our kids + my husband and I have a thread that has gone on for years. On my devices, it shows the other three people, but not me.

Last week, one of the kids sent a message to the four of us and it suddenly showed my name to me in the group at the top of the message. It not only reached all four of us as a thread, but it also came to my i messages as a single message. And when I responded? That came to me individually, too.

When I respond to what appears to me to be a "new group," it shows up in everyone else's "old group." They only show one thread, I show two.

I have tried deleting the weird new thread, turning i message off and on, resetting everything, and still it persists. Has anyone else had this happen?

It's making me a little crazy. Just a little, though.