Though my grandma has a great belief and wanted my sister and me to follow in her footsteps as well, I never was a believer or had the right idea if he existed or not. I simply could not find an answer for this as I started to think about it. (my sister is another story, but she didn't start it for grandma, but for that she was interested in it and after found friends there and feels so good, and I'm glad to see it, I find it good that this brings people together)
I still don't know if he existed or not, but it doesn't interest me that much after, not to mention in my opinion this is the way it should be. If ppl could proove he existed, that would hardly change the world and cause dramatic efects in some ways, but the opposite would have the same effect as well. Still I can think of that he existed, but I can't imagine him as son of god or someone who can do special things, but someone who just tried to make connections and be nice to ppl in those dark days... Someone who helps ppl with being nice to them, like he always smiles on pictures and looks calm as well; and help them solve their problems by giving them the chance to tell these to him. (er, with a strong resemblance he was like some psychologist, but in the very positive way)