What TV series did Robert Conrad and William Conrad do together?

William Conrad (Sept. 27, 1920 - Feb. 11, 1994) and Robert Conrad (b. Mar. 1, 1935) were never in a TV series together. They were in the 1971 TV movie "D.A.: Conspiracy to Kill" together, and they each had parts in the 1959 TV series "The Man and the Challenge", although they were in different episodes and did not perform together.