My 7 yo DS is named August, we've always called him Augie. He's named after my grandpa who was called August most of the time, but was called Augie by some - which is part of why I picked that for a nickname when he was born (August sounded way too formal to me for a tiny newborn).
He just asked why I didn't pick August as his nickname and said he wants me, DH and his little brother to call him August from now on. I'm not surprised since he told me a few months ago that he was planning to go by August when he grew up. I'll need some reminding, but its his decision! Plus, I obviously like the name since I chose it for him. :)
Right now he doesn't care what anyone else calls him, but I wouldn't be surprised if he wants to be called August by everyone in not too long.
Have your kids ever decided they wanted to change what they are called?