Did one of Don Knotts brother play in an rosode of gunsmoke?

Yes, Don Knotts' brother, William Knotts, appeared in an episode of "Gunsmoke." He played a character named "Joe" in the episode titled "The Jailer," which aired in 1964. Don Knotts himself is best known for his role as Barney Fife on "The Andy Griffith Show," but his brother also had a brief acting career.