Don't know a decent way to do it, but a roundabout method would be to give the current ruler some sort of flag. When the ruler dies, an event would then fire for the next ruler that removes the title and this event would be triggered by a ruler not having the flag. If that makes any sense.
Yeah thought of that but I'm trying to avoid even that. I was wondering what you can do with succession law, such as make a custom succession law, I haven't messed around with it at all yet.