Vaughn is married, let me tell you all why. Most sitcom's always save the long struggled relationship till the very end, usually with a wedding. Usually the sexual tension between characters and their struggle to be together is what keeps a show interesting. It has been proven that when two characters in this struggle begin a relationshp early (like first, second, or third season) then ratings go down, because there isn't any conflict. The Alias writers gave us enough of Vaughn and Sydney to satisfy all of us Sydney and Vaughn lovers. But they were smart to split them up to cause more conflict and keep viewers tuned in. This was discussed in on of my Film/Television classes. So Vaughn mostly likely (I can't say 100%) is married.