Not a thread about a thread, just inspired by the other thread as it made me think and I didn't want to hijack.
My uncle remarried two years ago after my aunt died. His new wife - who I don't see as my aunt because I don't know her and I'm too old to use it politely, I don't have a problem with her - has three children, the youngest is a teen and the oldest is a parent herself. Her ex is still around, they still have regular contact with their dad.
We were at a family party recently and my uncle went over to where his wife was sitting and she said to one of her children "move up and let your dad sit down"! I was really shocked and my parents told me it wasn't an accident that's how they - uncle and his wife - refer to him! My uncle was married to someone else when the youngest became a teen so it's not like he's brought him up or this is a small child who doesn't know his dad.
My partner has other children and there's been times he's felt the new partner has said something he shouldn't but I think he'd be gutted if whilst he's still involved and an active part of their life if the new partner was being called dad.