I think it said she was the mom of one of the 3. There is no history anywhere of step mothers not treating their husband's other kids well, so I am sure everything is fine.
"Be bold, and mighty forces will come to your aid."
For the last 14 years of his life, he was in a relationship with costume designer Mimi O'Donnell, whom he had met when they were both working on the play In Arabia We'd All Be Kings in 1999.[9] They lived in New York City and had a son born in 2003, and two daughters born in 2006 and 2008.[137] Hoffman and O'Donnell separated in the fall of 2013, some months before his death
Well, at lest there's that. So basically he left his fortune to the mother of his kids, whom one would assume would take care of the kids. Sounds about right.
"Be bold, and mighty forces will come to your aid."