Ceres' truth magic potential, reveal itself when he was around 4-5 years old, just a tiny bit earlier than most unicorns do. Actually when he was just a toddler he lifted his father without effort, but nothing esle until much later. The important thing here is not when his magic revealed itself or what spell he was casting, the important here is the magic scaping from his tiny body. Ceres couldn't hold all that magic so whenever he uses a simple spell like lifting some books, a lot of magic is released in the form of a breeze.

It didn't took Twilight too long to notice all the magic he was wasting with some lame breeze, so she had to train her baby to become the greatest unicorn in the whole world, even better than Starswirl himself. Yeah we're talking about her child let her dream.

This is a redraw of this