Matt was busy perusing the book so when Teddy wiggled his way under his arms he hadn't been prepared, not that he needed to be for a hug from his brother. The Riley family was an affectionate one. He frowned a little when Teddy did that thing he did when he wanted reassurance and to know Matt was there and Matt simply wrapped his arms around his little brother.
It was silent, but reassuring and grounding.
And then he gave a small burst of laughter and shot his brother a smile as he signed in return love you too before giving Teddy's hair an affectionate ruffle.