I didn't say they were all dead, I never used words of certainty, I said likely. Did you misread me? Because it looks like you corrected me... by saying what I said. (Not annoyed, just confused.)
As for children, it depends on how openly this boy was kept while he endured years of torture, malnourishment, and abuse. If he was M's adoptive brother, she's no longer with us. If he was a 'hidden' child because of disability or abusive dynamic, unless he had siblings who were similarly treated, they may not have known he existed. If they were similarly treated, they may also have died of their treatment.
We won't know anything with any certainty until the press release, and even then, there are likely to be things we never know. It was a very big secret for a very long time, and, like I said, those who may have known this boy in life are likely - but not certainly - dead.
MOO