Talking to Grandpa

My best non-human friend Buster died a year or so ago after a long drawn out illness, he was almost 18 years old.  On his last day we knew it would not be much longer for him. He was not in pain but he had stopped eating or drinking. That morning he followed me around from room to room and would lay at my feet. Every time I reached down to pet him he would look up at me, purr and smile (yes smile). I have had other cats but they were just "cats". Buster was a little person in a cat suit. I don't care what anyone says Buster and I had a relationship. 

A few days after he was gone I was feeling very sad and missing him. I was talking to my son about how much I was hurting. He told me how much he missed Buster too but that it was okay because he was in heaven. I asked how he knew that and he told me "Grandpa told me".  This threw me for a huge loop as my father had died two summers before.  I said "Grandpa told you, what do you mean?" He said "Well I was feeling bad about Buster and Grandpa said not to worry cuz he had found his way to him in heaven and they are together now and everything is alright" I am seriously freaking out at this point but trying to remain calm. Maybe this is just a childhood fantasy phase that will pass. Or is he like that kid from Sixth Sense only "I talk to dead people" or is this some new psychosis I have to keep tabs on or should I sign him up for his own cable show ala John Edwards, "The amazing Kid who converses with the hereafter"? I asked him if "other" people talked to him too, thankfully no, just Grandpa. I am torn between worrying and immense sadness at the loss of my Dad and that he doesn't talk to me, if he could. 

With tears threatening, in my calmest "tell me all about it" motherly voice I ask him about talking to Grandpa. He says he talks to him a lot that Grandpa tells him stuff. "Like what kind of stuff?" I'm thinking the worst put the cat in the microwave crazy talk. "Like about heaven and sometimes when I'm at school I'll ask him what 100 times 100 is and he tells me or sometimes when I am scared at night he tells me it's okay to be scared but I don't have to be cuz he's there, you know stuff like that" and he shrugs his shoulders so nonchalantly like "hey it is no big deal that my dead Grandpa talks to me"  I have no idea how to respond to this. "What does he tell you about heaven?" He smiles "He says it's nice and now Buster is there it's better". My brain can not wrap itself around this. Why does he think Grandpa talks to him? Does Grandpa really talk to him? Stranger things have happened right?  I just say "That's great honey, I'm glad Grandpa talks to you". I don't want him to feel weird about it.

I asked him recently if Grandpa still talked to him. He said "not so much anymore". I can't decide if that is a good or bad thing.  Has he passed through this phase or has some unseen door closed?