My gf 49 and me 54m live separately but see each other several times a week. She has two kids 13 and 15 both girls.
The kids have been fatherless almost all their lives and mum brought them up in a happy loving house where each morning starts with them bursting in and leaping on the bed for chats and cuddles from mum. They will also just burst in in the day.
So, you see where this is going. There's no lock on the door and the kids have no boundaries. The eldest daughter has nearly caught us several times and I can't wrap my head around it.
If I had suspected my parent was having sex or had a gf or bf in the room, I'd knock and wait. Id also not come in till I was absolutely sure I wasn't going to interrupt.
In context, the older one is a narcissist personality disorder with sociopathic tendency. They younger one autistic with very poor learning or social skills.
So , looking for advice, beyond the "ask mum to set boundaries" as that moment passed a long time ago.