I think Bob Joyce is Elvis's "dead" twin Aron.1935 was during the depression.It was not uncommon for poor families to give up 1 of a set of twins that they couldn't afford to keep.I think his mother felt a great deal of shame and regret over this,hence the lie.
So of course he has physical markers that match Elvis,voice with 98% match,and has been seen at Graceland with family and friends of Elvis.If you found out you were adopted,and had a very famous dead twin,how else would you get to know him?I think there is an NDA to protect Elvis's mother's privacy.Elvis loved his mother.I think he knew the truth and dyed his blonde hair black when he started to get famous,to protect her from that twin being recognized and people putting 2 and 2 together and exposing her to public shame.
Bob's answer to the direct question are you Elvis? Makes perfect sense in this context......he is who God meant him to be...the long lost twin of Elvis.