This is story related and cannot be missed.The moment you first start the game, run left and into the water to get:
Now, restart the game, and run to the right following the mini tutorial. After going over the seesaw and down the slide, this achievement will unlock as you continue to progress to the right.
When your brother is stuck on the roof trying to get his kite, don't forget to approach him slowly and jump over the hole he makes when he falls through the roof, so you can continue to the right, climb the little ledge, jump towards the kite and unlock:
Happy hunting!
~M~