Whatever the show the girl had put on inside of his brother's head, it looked to Emmett like it must have been the genuine article. Edward's expression was a complete 180 from the skepticism and doubt they'd both been sharing just a few minutes before. In fact, his "little brother" was smiling. Smiling. And not only that, he was telling Renesmee that he was going to try and be her dad.
If Emmett had been breathing, he'd have let it out in a disbelieving "huh".
When the girl offered her hand to him, Emmett was lined up in a blink. "Yeah, yeah," he said, making contact. There was just no doubting the stuff that flew through his head, like a movie on fast-forward that he could still understand. If he'd thought Edward smiling a second ago had been amazing, the sight of him as a husband and father was totally unbelievable.
Once he stepped back, Emmett laughed, loud enough to shake the house. "Well, welcome to the family, I guess!"