Unofficial Oblivion Patch

Although it would line up with the behavior with his brother and sister, as well as with the actual dialogue line, and the attached developer note, Matthias does not have any coding attached to make him go hostile after he tells you "Slave of WHAT? Oh, all right, then! You're some kind of crazy, is that it? Come here then! Show me what you've got!" It's possible that his other line "What? A dead man? You got some kind of death wish, is that it?" was also meant to make him go hostile as it also causes a disposition drop and would line up with his established brash personality.