IOS 12 combining text messages

After updating to IOS 12 my IPhone is combining text messages from family members. My wife and I had a text going and then my daughter got added to it & then my son got added. Each phone has only their number under IMessage as a Send/Receive and each person can only see the messages they send and my response. I can see all the messages from each person and my response. When my wife sends a text it has her name but once my son or daughter send their text the text message changes to their name. We only have one Apple ID for the family but i've been reading that might be the problem. Under Apple ID their are a bunch of number listed including my wife, son, and daughter's numbers so I was thinking about deleting them from my Apple ID but I don't want them to lose any text messages or other information.