I don’t know much about M’s story, but if her mother bought him, did she say for what reason? To be a member of the family? To eventually work for the family or some other nefarious reasons? I don’t think the mother could collect welfare for him.
If it was for the first reason, surely there were photographs and other family members and neighbors who knew of his existence and yet from what I read, she couldn’t corroborate her story.
It does seem like he was hidden from an early age by whoever his caregivers were, unless, he unfortunately, wasn’t recognisable to those who had encountered him at one stage, in his very short life, so they never came forward.