Boy discovers he's a clone used as a body part backup

Hi,

Think it might of been a reddit thread on like r/nosleep or something similar.

But teenage boy discovers he's a clone of a mega rich billionaire who uses him for spare parts. So the rich guy would lose a leg in a skiing accident then the boy would pass out and wake up without his leg and he had a fake mother who he thought was his real mum.

Only ever read the start of it but its an interesting premise. Any help much appreciated