Marvin was born in Dover, Oklahoma to Maydrene (née Paulsey) and Roy Webster. The family, including Marvin's sisters Marie and Carrole, moved to Davis, California in 1951. Marvin attended Davis High School and graduated in 1952. After being drafted into the Army Engineers Corps in 1953, he served in Korea before being discharged in 1955. Returning to Davis, he began working as a painter for the University of California, where he dedicated 44 years before retiring in 1991. In 1956, Marvin met Ruth Santos, whom he married in 1965 and later had two sons together.
Survived by his wife, Ruth, Marvin leaves behind sons John (Barbara) and Ken (Amy), grandchildren John Webster Jr. (Shelley), Kayla Beers (Clayton), and Amber Webster, as well as great-grandchildren Julia Wease, Chase Beers, and Adalyn Beers. He is also survived by his sisters Marie Anderson and Carrole Haas (Bill).
Marvin was known for his talent as an artist, his passion for corvettes, and his role as a dedicated surrogate father to numerous teenagers. He touched many lives over his 90 years and he leaves behind a profound absence that will be felt by many.