I see from his biography that "Moon took lessons from one of the loudest contemporary drummers, Screaming Lord Sutch's Carlo Little". I lived two doors down from Sutch fortunately he stopped practicing in his garage and started practicing at Ginger Baker's house about half a mile away - that was soundproofed.
The Wikipedia article names Moon's parents and the BMD registry shows potential siblings:
Births Sep 1946 Moon Keith J Hopley Willesden Births Jun 1949 MOON Linda M HOPLEY Willesden Births Jun 1958 MOON Lesley A HOPLEY Willesden
Keith J Moon
England and Wales Birth Registration Index