Mm. The Prince before me was like that. He forced me to kill him before I could get rid of him - and by forced, I mean he threatened to kill a bunch of innocent people if I didn't, and the condition was explicitly "kill him first". I think he believed he was doing me a favor.

[He just sighs.] It's probably a good idea if you stick with him anyway. Losing enough blood to keep two vampires fed on a regular basis would probably make you useless for anything else anyway.