Brainiac 5
Originally thought to be the descendant of the original Brainiac, Brainiac 5 is actually descended from Brainiac II (Vril Dox), who was adopted by Brainiac I to hide his origin.
Brainiac 5 (real name: Querl Dox) is a member of the Legion of Super-Heroes in 30th Century Metropolis (Act No. 276/2, May 1961: "The Three Super Girl-Friends"; and others). Possessed of a 12th level intelligence commmon to his homeworld of Colu, his many inventions have included the Legionnaires' time bubble, the cure for Mon-El's lead poisoning, flying belts, flight rings and Computo.
Both Supergirl and Brainiac 5 applied for Legion membership at the same thing but Supergirl was rejected as Red Kryptonite had turned her into a Superwoman and over the 21-year age limit for membership (Act No. 276/2, May 1961: "The Three Super Girl-Friends").
As depicted in The Chronicles repeatedly, Brainiac 5 and Supergirl are sweet on each other.
Note: the original future timeframe of the Legion of Super-Heroes is chronicled as the late twenty-first century, hence only four generations seperated Brainiac 5 from his namesake "ancestor." The bulk of the Legion stories are firmly placed in the 30th century, and the character's name is unchanged.