I can tell you with absolutely no doubt that I didn't betray Lily and James, that if I had the power to magic back in time and never change Secret Keepers, I would. (And still kill Peter for good measure.)

After that... everything I know of Peter staging his death and killing those Muggles, about being locked up and for over a decade, of Regulus not being a Death Eater after all, that's all stuff Harry's told me. I believe him, or at least I want to believe him. That's all I can say.