There are twelve avatars, and the thirteenth which is Death.
It is normal for the royal family to produce fewer than twelve children in any generation. It is rare that there should be a thirteenth.
Thus there is no difficulty when an older child takes it upon themselves to walk down to the pit of the avatars and jump.
For example, one cannot consider Cedric selfish in any manner for taking the first of the twelve avatars.
When he made his choice he was fifteen and he had three siblings only. His condition was one of abundance. He walked down to the avatar pit. He stared down: the pit was deep and black and full of edged in sharp rocks. It resembled an ecstatic’s vision of the entryway to Hell. Cedric steeled himself against fear. Then he jumped.
As he fell he connected to an avatar. This proved his blood and confirmed him as a child of the throne. Great black wings surrounded him. Stars burned around his head. In this fashion he became one with Night.
Very cool. Check it.
Terrifying thought: Rebecca Bergstrom as your GM.
Equally terrifying: she’s one of your players.