Not sure.

*He puzzles over it, frowning. He remembers the man clearly, of course, from when he was presented with his own wand: fir, Ollivander had said, is a wood of extraordinary resilience, suited to a survivor. He'd almost looked through Peter with those pale eyes of his, and hadn't elaborated.*

He seems pretty...Neutral? Singleminded? Not sure what the word is. But I don't see him being a loyalist.