I find it odd that you'll protect your brothers when you don't even know who they truly are. I may not be blood-related to Constans, but he is my friend and I am certain that I know him more than you ever will, especially now.
My letter can contain anything, Bann, and while you are correct the Circle may not bother... it will be stored for when your armies may need some extra help from the Circle and considered in the decision making process.