Okay, I'm playing DV 2.1 beta with DVIP, DVIP Addons, and the DVIP Wales pack, and I started a game as Duke of Gwennyd. Since I had a claim on the duke of Deheubarth, I started a war against them about 3 years in. I completely invaded both of his counties and went to the sue for peace screen. The only thing I could ask for was the duke of deheubart title, I couldn't vassalise him or anything, so I took the duke title and took 58 ducats. I assumed that since I'd be duke over him, that'd make him a count vassal, but no. I got his bishopric vassal as my vassal, but he continued to be a 2 county sovereign count. How do I make him a vassal? Do I have to invade him again as a count so he can be my vassal, since we were both dukes back then? Is that why? Honestly I can't tell. Can a Duke vassalise another Duke and take his Duke title away in the same peace treaty?