Both Jesus and John fulfill prophesy! Though that does not prove they knew each other prior to encarnation, both of their births have highly unusual circumstances. Jesus, born of a virgin. John born of a much older, formerly barren, woman and her aging husband. Kind of reminiscent of Abraham and Sarah.
There are others with, not normal for humans, origin and existance such as Melchisidek of whom it is said had no parents, well if not where do these mysterious persons come from? Then there are mysterious departures too.
So it seems, that which is not explainable according to the norm could in fact be explained by the unusual.