What I said, sounds like the (villain) protagonist and his cousin from Gibo (hentai game), it's started as mutual benefit and comfort, though they do have genuine (but extremely messed up) romance later.
This is supposed to be initial design of Panzer Igel and Northwind Messiah (Compact type I.S.), but the armament is a bit different than what used in the fic. I'll trace it given enough time, but currently I'm still busy doing reports
As you see, inspired mostly by Alteisen and Weisritter
