Board Thread:WARNING ALL USERS False Info\Spoilers/@comment-11260666-20140122174506/@comment-25178327-20140123014813

Isaac likewise had an older brother who died (as an adult) in Iraq. But the protagonists are only-children. Isaac's brother is not comfirmed as dead, Matt simply said "Camden, Laheys Jarhead son". So he could still be alive, yet I'm pretty sure he would visit Beacon Hills after his Father died  to take care of Isaac, so you're most likely correct.