sounds more like something royal siblings would do to each other. since neither one has the power to have the other killed for the offence. they compete for the heir lol.
Although, in reality, if you're actually competing to be heir to the throne and you're secretly hiring assassins to kill your sibling, then no one is going to be happy about it.
One, you're trying to kill your sibling. He's not going to like that.
Two, it's completely illegal even for princes, and members of royal families have been executed for it. So you're not going to be admitting to doing it, so there won't ever be a friendly spin on it.