How to leave your own kingdom?

I want to help out a claimant but it won't let me because it says i'm a king/queen. is there a way to get out of your kingdom without other factions going to war with you and then losing all ur land to them?

Ummm.. I don't think so, there might be a feature in Diplomacy 4.1 mod, but in native the only way to get out of your kingdom is to go to a king of another faction and trying to join them, although you hand over all of your territory to them and if you're lucky (and male) you'll be able to keep a place or two.

AA's got it right, though I don't believe Diplomacy changes this.
(Stickied Q&A thread would have been perfect for this.)