Yes, to an extent. Imagine a decision you made in your life. Now imagine how your life would be different had you made a different choice. For a while some of us were swapped with other versions of ourselves, those who made that other choice. This man, as I understand it, has two personalities inside his head. When we met this Lord Harry version before, it was technically a different version, but essentially the same man.
I, personally, don't trust the demon at all. But others might, others who know him better than I do and have seen his actions up close.
It's possible. It's happened before, once that I know of.