The whole heir thing gets so messy because it's never just about raw power. I get why authors love it – it's pure tension. You've got the weight of the family legacy, which is basically a gilded cage. They're trained from birth in this very specific style of magic, and any deviation is seen as weakness or rebellion. Meanwhile, the younger siblings or cousins who might be more naturally talented get sidelined, fostering this deep resentment. They either become the hidden weapon or the scheming antagonist. And let's not forget the political marriages! The heir's love life is rarely their own; it's a tool for alliance, which is a classic source of conflict if they fall for someone 'unsuitable.'
Honestly, the best conflicts come from the heir rejecting the dynasty's core values. Like in 'The Jasmine Throne' – the heir refuses her family's oppressive fire magic, seeking a different path. That internal war between duty and self is way more interesting than just another duel for the throne. The magic system itself often becomes a character. If the dynasty's magic is tied to, say, blood sacrifice or exploiting land spirits, a morally conscious heir is stuck with an awful choice: uphold a terrible tradition or let the family's power crumble.