Whenever i change one of my contacts information it changes mine too, and vise versa

So basically, my brothers contact is weirdly connected to mine and i cannot fix it. Whenever I change any of my information in settings like my photo or my name, it changes his along with it, and if i change his photo or contact name, it changes mine. I have tried everything to try and fix this, going to account settings on contacts and everything. Its doesnt happen on his phone or when he changes his own information on his phone in settings, just mine. I only started having this problem like two or three years ago. Even after getting a new phone i still have this problem. Someone please help!!