In Chapter 6
After you encounter the turtles, when you come up to the area where you need to chop down a tree to create a bridge. Keep to the left and go up the hill.
You'll see the saw you need to cut down the tree. Keep going past that. You'll see another bench. Sit on the bench with both brothers and enjoy the show.
I found a YouTube video that shows how to get this achievement/trophy. I didn't make it.