Just throwing a thought out here...I know it has been speculated by many, including if I'm not mistaken M herself? that BITB may have been secretly fathered by M's uncle, which would make him M's biological cousin . Now, if we are assuming that that information is correct (I guess we may find out?), maybe BITB was born to the daughter of a promeninent Delaware County family and M's uncle. On top of this, he may have disabilities or developmental delays. M's uncle is uninvolved with his life, the mother's family sells him to M's family, to keep him at least with his father's family, and washes their hands of him, so to speak. It explains him being traced to that family at least.