Does Sigourney Weavers mum call her Susan for example?
I think some famous people change their names across the board, and everybody then calls them that, whereas others only ever use their stage names professionally and nobody ever calls them that in private life.
I'd love to think that some of the musicians, who don't just swap one plausible-sounding name for a different one (albeit more glam-sounding) but go for something more abstract, have mums who now call them by their stage name.
"Badly, your dinner's ready!"
"50, we need to walk out of that door in 10 minutes!"
"Vanilla, did you remember to put some petrol in the car?!"
"Ol' Dirty, don't forget it's your Nan's birthday in two weeks' time!"
Possibly surprisingly, Meat Loaf (born Marvin Aday) has always (since changing his name) been called Meat by everybody, even in private. It's two distinct words: first name Meat, surname Loaf. His ex-wife went by the name Lesley Loaf, but their daughters both use Aday.