Must be his mother -- née Sherman, a name that can go either way.
His parents named him after Woodrow Wilson (wikid) and he married a Juess. He died of Huntington's, of course, and "Guthrie's early family life was affected by several fires....... It is unknown whether they were accidents or the result of actions by Guthrie's mother Nora, who was afflicted with Huntington's disease,[8] although the family did not know this at the time. It leads to dementia as well as muscular effects." If they can call us criminally insane, we can question their mental state.
The year after he died, Arlo starred in Alice's Restaurant, one of the worst movies EVER made, which portrayed him giving his very sick father a smoke in the hospital.