The gens was always said to have descended from and been named after a mythical personage named "Iulus" or "Iullus", even before he was asserted to be the son of Aeneas; and it is entirely possible that "Iulus" was an ancient praenomen, which had fallen out of use by the early Republic, and was preserved as a cognomen by the eldest branch of the Julii. The name was later revived as a praenomen by Marcus Antonius, the triumvir, who had a son named "Iulus". Classical Latin did not distinguish between the letters "I" and "J", which were both written with "I", and for this reason the name is sometimes written "Julus", just as "Julius" is also written "Iulius".