I have a good friend, Richard, who is a top-notch musician. He plays piano, sax, clarinet, harmonica and even bagpipes, and he sounds almost exactly like Ronnie Milsap when he wants to. He and his two brothers are all blind, all excellent musicians and all have perfect pitch. They can play in any key effortlessly.
I asked him once about having perfect pitch and he told me that he "sees" the notes like colors; in other words each appears differently in his brain. He quit the traditional music business some years ago and became a minister. He does play a lot for his church and other worthy functions.
One of his brothers, Talmadge. has unfortunately almost lost his hearing, and that's a real tragedy.
When Richard used to work with me, I would try to fool him by hitting dis-chords but he could tell me immediately every note I hit, even when the chord was not musically correct. He also used to program my drum machines, and he was my "sound engineer" and would help me set e.q., etc., and then tell me "don't touch it".
Side note: One time when he wasn't working with me, his sister came in. I had never met her until she introduced herself. I asked her if she sang and she said yes, she loved to sing.
So I invited her to sing a song with me, and ...she was absolutely terrible. Couldn't hit a note on key to save her life! But she could see . . . maybe music talent could be some sort of compensation for physical disabilities in some cases.
Rory, Ray Charles, Milsap, all seem to have this talent.
I know the brothers all had early training in music theory but you can not teach perfect pitch.
Sorry for rambling.