Michael McCain suffered from three broken ribs, a broken leg and a fractured arm from the fall into his basement. Hannah McCain and the rest of Michael's family assumed that Michael had been trying to play down there when he fell and suffered the grievous injuries. The family also assumed that the injuries, coupled with the grief of losing his father and brother had caused Michael's muteness. As of July 25th 2018, Michael McCain never spoke again.
The police assumed that Matthew McCain had died in a car accident caused by his drunken driving, but couldn't be completely sure as the body had been severely mauled by, presumably, the abundant wildlife surrounding the crash site. The police also assumed Matthew had taken his youngest son, and the body must have been carried off by the wild animals that mauled child's father.
Hannah McCain moved away with her remaining son, and never returned to the house in which they had lived.
The body of Charlie McCain was never found.