I found Hugh's death certificate in 1918 - at the address where his family was enumerated in 1920 - and added it to the profile. It names his father, but not his mother.
Familysearch's PA death certificates seem to stop in 1915, but Ancestry.com's run to 1968. At one point they used to add another year's worth annually to keep the collection up to 50 years before the present, but that seems to have stopped.