Prince William of Wales

When he was young, it was an unofficial rule that he could not fly in the same plane as his father because an accident might take the lives of two future kings. The sovereign must give permission for two heirs to fly on the same plane, which was occasionally granted.

(about becoming King) I am worried about it, but I don't really think about it too much because there's no point in worrying about things which are not really present yet. It's not that I never want to do it, it's just that I'm reluctant at such a young age to throw myself in at the deep end.