Vox Akivasha

Primarily, he looks up tremendously to Akivasha as a powerful mage, and wants to follow in her footsteps. The problem is, he can't cast for beans at this point. This frustrates him tremendously, and as time goes on he starts lashing out and rebelling - he even ends up blaming Sully for a time, thinking that his antimagic affected him and disabled his own magic. (In fact, in my original concepts, this is exactly what happened - the concept has pretty much revolved around 'Child who looks up to mother's magic but has some sort of struggle achieving it')

Now obviously that isn't the case, but he ends up forming a negative feedback loop with himself. When he lashes out, he gets emotional - and when he gets emotional, he starts to see sparks of magic. They're just very minor and uncontrolled, but it encourages him to act out more.

The actual issue is pretty multi-layered. For one, he's just a kid, so his emotions are A Mess by default. But it's not just that - he's surrounded by responsible, noble, and powerful people who all possess a sense of calm and control. He's actually suppressing his emotions because on a subconscious level, despite his outbursts producing magic effects, he has the idea in his head that displaying emotion is a Bad Thing. Furthermore, for most mages remaining Calm is a cornerstone of casting technique, which just goes to muddy the waters even more. He's fighting back intense emotions that he's experiencing and stifling himself in just about every way.

He also has a habit of abusing his Sanguinuity, for lack of any magic skill - which leads to a lot of scares. Both on the end of him passing himself out, because the Akivasha line's is Explosive - and scaring the crap out of anyone he may threaten with it. He never actually intends to harm anyone of course, but it's a scary display of power

Finally, after some time he latches onto music, as an outlet and just as a general enjoyment and passion. He actually sneaks out quite a bit to partake in some of the City Culture and ends up involved with the youth music scene. Music ends up being a way he can feel safe in expression, since you're "Supposed" to do so. So he starts dumping all his dammed up emotions into his music. Sully makes him a set of headphones, and it's that point he starts showing his actual magic potential and things become a lot clearer. One imagines the people around him are all trying to figure out what's going wrong or not clicking, then one day he lights the curtains on fire while belting out a screamed line, or causes a small earthquake while air drumming.

It's prooobably about between 8-10 years old they figure this out? But there are some further complications to his magic style from there. For one, he has to actually learn to engage with his emotions in a healthy way, understand and to an extent control them. One major issue is that at first, when he does cleanly harness his emotions - the effects are largely uncontrolled, similar to Sherri's random magic bursts. If he strongly feels an emotion, he may cause a magic effect unintentionally. He has to take a lot of time to train more aspects of his life and casting style than most mages may have to. As a result, he Meta's later than most - early to mid 20's, most likely, instead of teens.