Re:Double bodyweight deadlift @ 8 years old
fantastic, just be careful he doesnt get too serious while hes still young, as he needs to have a life as a kid.
but then again what kid wouldnt wana be 3 times stronger than everyone on the playground hahah
also, dont get discouraged if his weight/growth starts messing up his bodyweight/best lift ratio, i.e when hes 35kg he'll needa lift 70 to hold onto that double body weight title, and it may be a tall order eventually.
best of luck for him in future, keep pumping !