Matthews played four seasons for the San Francisco 49ers (1950, 1953-55), and was the patriarch behind one of the most famous family trees in NFL history.
Both of Matthews' sons, Clay Matthews Jr. and Bruce Matthews, were named first-team All-Pros multiple times. Bruce was inducted into the Hall of Fame in 2007, while Matthews Jr. was a semifinalist in the 2017 HOF class.
Clay Matthews Jr. and Bruce Matthews also each have two sons who have played in the league. Clay Matthews Jr. is the father of Packers linebacker Clay Matthews III and former Eagles and Vikings linebacker Casey Matthews. Falcons left tackle Jake Matthews and former Titans, Redskins and Panthers offensive lineman Kevin Matthews are Bruce's sons.
All in all, Matthews Sr.'s lineage is the third-ever third-generation family to play in the NFL, per the Pro Football Hall of Fame.