User blog comment:Rassilon of Old/Silhouetted characters on the Young Justice: Invasion poster revealed!/@comment-3118271-20120505211218/@comment-99.189.12.150-20120506132509

If you read the comic books you'd know that barry allen flash traveled to the distant future, had a kid there, that kid grew up in th future and eventually had a kid of its own. Eventually the grandson traveled back in time to the present to get help from the current flash, then took the identity of Impulse.