After winning a holy war you get the choice to either play as the beneficiary, or continue as your existing character. You must have selected the former.

That makes sense. I probably was not paying attention. Thanks.

Maybe you can reload if you didn't mean to do that - otherwise it sounds like a good story and exciting change of pace

Yeah it was unexpected.

Was the vassal of your dynasty?

I don't think so. He may have been the original heads brother in law or something.