Group Chat screwed up after a member swiched from Android to iPhone
My family and I have had a family group chat for a long time. All of us had iPhones except for one of my brothers. Recently he switched from Android to iPhone and now the group chat is screwed up. Some of our phones show 3 different group chats with the same people in all three. Some of our phones show 4 different group chats. On one of the threads my dad can respond from his iPad, but not his iPhone. Depending on who is sending a text, the messages come in on different group chats so it's not one consistent thread like normal. We've tried deleting all of the group chats and starting a new one, but that hasn't helped (eventually the 3 or 4 different threads returned). We've tried removing different people from the group chat and adding them back. We've tried restarting our phones and making sure they're all updated. If anyone has a suggestion please let me know!
iPhone 16 Pro Max, iOS 18