I don’t mean in a good way, sense of humour, not taking life too seriously, I mean adults acting like children - sulking, answering back, causing trouble...
My MIL has held a vendetta against an exBIL for 20 years. She talks about him like a catty 13 year old. She lies to get him into trouble.
My FIL is a classic answererbacker, like a 5 year old and argues like a child (“I never said that! You take that back! I’m gonna tell DH!)
Why do some people get adulthood and others don’t?!