Factual error: No judge would award guardianship of a person with something like autism to a sibling who's a recovering alcoholic and drug dealer.
Suggested correction: I think it is POSSIBLE, but not probable. Someone on the spectrum may have poor coping skills when dealing with strangers or would not do well if placed in an unfamiliar environment. Placement with a sibling - even one as you described (recovering alcoholic and drug dealer) - may be less traumatic and disruptive than with a non-relative or stranger. A judge would have to weigh the bad against the good while considering the person's needs and the sibling's ability to meet or exceed those needs.