Was Lizzie Borden on Robert Mongomery's side of the family?

No, Lizzie Borden was not on Robert Montgomery's side of the family. Lizzie Borden was a historical figure known for her infamous trial for the murders of her father and stepmother in 1892, while Robert Montgomery was a well-known actor from the 1930s and 1940s. There is no direct familial connection between them.