Sabrina & Sirius.
Now, why the fuck would that make me mad? That's genius. Enormously brave, too.
You're not doing it just the pair of you, though. That would make me fucking furious. You need people around to stop him if he takes too much, for his sake as much as yours — your blood could poison him, we don't know.
And it shouldn't just be you who's doing it, even if you can sustain him longer — you're not the only non-human around who can chip in. My blood's normal magical blood, but he can drink from me if he needs it, I don't mind.