No, they are not brothers. Chuck Connors’ (born as Kevin Joseph Aloysius Connors) sibling is a girl named Gloria.
Mike Connors’ of "Mannix" real name is Krekor Ohanian and was actually sorry that he changed his name. People get him mixed up with Chuck.
Chuck has four sons and one of them is named Mike though.
Chuck was born to parents Allen and Marcella Connors, immigrants from Newfoundland, on April 10, 1921.
Chuck Connors was a former professional basketball and baseball player. He starred in basketball at Seton Hall College in New Jersey and played for two years (1946-48) with the Boston Celtics. He switched to baseball after that, playing briefly for the Brooklyn Dodgers and the Chicago Cubs.
Chuck died of lung cancer at Cedars-Sinai Medical Center in Los Angeles in 1992. He was 71 years old.
Of interest, find out 18 Cool Siblings In Hollywood You DIDN'T Know About from Refinery29.com.