If I am not wrong, there were only four children haunting Purple Guy to the suit in the mini game, the one walking on his own being who I think is the main bully of the son, his brother. However, there were six dead children, one of which is Puppet and the bullied son. I think the son is guilty that his father is haunted and doesn't join in to kill him, so he doesn't.

I am pretty sure this theory is absurd, so please don't judge and please give me ideas!