Michael didn't truly believe Sarah wanted to be with Cody but he still found himself panicking. She couldn't do that anyway; he would never go along with it. He was married to Karli and, despite his lack of enthusiasm about suddenly finding himself a father of three, it was clear that he loved her more than anything.
He hadn't wanted to get married in the first place but had done it to keep her with him as far as Michael knew. That was quite the dedication. It made sense though considering she knew the truth about him and accepted it. It was highly unlikely that anyone else would have been able to do that.
Hang on…was that what Sarah was upset about? It was true that all of their friends were married by this point but why would it matter to her that much? It was only a piece of paper.
He had already promised to always come back to her. Wasn't that enough?