Yeah, Jenn Garner got preggers so they worked it into the story that it was her and Vaughns *love* Only before they could get married Vaughn was "killed" by the bad guys. Only he wasn't actually killed -- he was very badly injured and then Sydney's dad faked Vaughn's death and hid him away so the bad guys wouldn't try to kill him again. The creator of the show, who isn't nearly as smart as he thinks he is, tried to make the audience believe that Vaughn was actually dead all this time, which was a whole lot of hooey.

So yeah, that's it in a nutshell ;)