Brothers a Tale of Two Sons

This is unlocked in the same area as Bunny Buddies in chapter 1:


You'll see that to progress through the level you have to go to the right and lower the bridge to proceed by using the treadmill . Across the bridge are some sheep. Pick one up as the older brother while the younger brother holds the bridge on the treadmill and bring the sheep back to where the rabbits are, now drop it on the same firepit in the middle to make the sheep black, and unlock the achievement.

This achievement can be unlocked in Chapter 1 after being chased by the dog in the field. Following the path will lead you to a new area. Follow the path, go down the ledge and you will see a wheel and a bridge in front of you. Use the little brother (RT & RS) to move the wheel to lower the bridge. Once the bridge is lowered, use the big brother (LT & LS) to cross the bridge and pick up a sheep. Cross back over the bridge and put the sheep into the wheel; this will lower the bridge again. Use the big brother to cross the bridge again and pick up another sheep. This time after crossing the bridge take the left path. Drop down the ledge and take the sheep to the fire pit. Let go of LT to make the sheep black and the achievement will unlock.

The achievement can be seen in my video guide: