I genuinely don't know!
DS is seven. He has a friend (8 years old) who lives 2 houses down. It's not a busy road or anything and he doesn't have to cross any streets to get there.
He goes often to play over there and occasionally the friend and his sister (she's 4) come here, although we're renovating so they don't come in as they'd have to sidestep piles of tile, lumber etc to use the bathroom or go up to DS's room. They do come play outside though.
DS went over there this morning around 9:30 and I went to get him around 1.
I saw the mother (I don't know her well but we say hello and she's pleasant enough) and said thank you for having DS and that I hadn't meant to leave him so late.
She said "oh it's fine, no problem at all" and then added 'I got to sleep in because he kept my two busy!"
I didn't really know what to say. In the first place I had asked DS if the friend had asked his mother before DS went over there, and he'd said that it was fine.
I have been known to sleep in when DS is awake if he's watching TV or reading, and I sometimes nap if DD (14 months) is napping.
But it wouldn't occur to me yo sleep if DS's friend was over and I assume DS and his friend were somewhat responsible for the 4 year old while the mother was sleeping.
I don't think I'm really comfortable with this...AIBU?