 He also elevated his own son Palladius to the rank of Caesar and had him marry Eudocia, elder daughter of Valentinian.According to those historians who believe that Olybrius was Petronius' son, it was in 455 that Olybrius married Placidia, between April 17, when Petronius was acclaimed Emperor, and May 31, when he died; this would explain the marriage between Olybrius and Valentinian's younger daughter as a move to secure Petronius' legitimacy as emperor.Another possibility is that Olybrius and Placidia were engaged in 455, and only after Gaiseric freed her from his possession in the early 460s were they at last married.