This is a common morning activity at our house-Hud building with Legos or playing with his "big ba-chines" and Chap scooting around the floor, putting things in his mouth. I love to see them interact and think they're going to be good buddies someday soon. For the most part, Hudson is very gentle, but every once in awhile I catch him sneaking over and trying to do a push-up over Chap.
But somehow, being the 4th child must make you pretty resilient. He mostly just smiles and squeals after that and goes right back to chewing his toy.