Here is the full list of all 12 Brothers - A Tale of Two Sons achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
You practised singing.
You found a secret.
You sounded a giant horn.
You re-united the two love birds.
Make a wish.
You took a break from adventuring.
You helped the turtles to the sea.
You made the inventor dance.
You made someone feel better.
Every family's got one.
You made the bunnies play nice.
You threw someone's ball down a well… Shame on you.