This was a ton of fun, and I ended up playing all the way to the end. The combination of the small and large character made for some fun puzzle solving. I particularly liked the part where you use big bro to push the comb-thing out of the way for little bro to make a jump. That was one of those perfect puzzles that make you feel like a genius because the game doesn't directly tell you to do it, you just have to critically think about it. Also having big bro played from a different camera angle was a great choice, especially when you started to add the poses to it.
The only real feedback I'd give is that the controls for big bro were a bit wonky. I would definitely have preferred something more like isometric controls where left goes left from the player's perspective, down goes down, etc as trying to remember which was W or S was going to move me was a bit tricky at times. But otherwise it was a fantastic game that made good use of the theme so great job overall!