 Seleucus was a Greek nobleman who was the son of the wealthy Cretan Flavius Ablabius, by an unnamed woman.His family was connected to the ruling Constantinian dynasty of the Roman Empire as his father served Constantine I. Ablabius was one of the most important senators of Constantinople; who held the praetorian prefecture of the East from 329 to 337/338 and served as consul in 331, who was active in public posts in both East and West.Seleucus had at least one known sibling a sister called Olympias, who was once engaged to Constantine I’s son, the Roman emperor Constans who later married the Roman client king of Arsacid Armenia Arsaces II (Arshak II).