The likelihood, should such a person have existed, that he is related is quite slim either way. When we consider that Ewing is from the same root as John, and Scottish naming conventions in the 11th century were similar to what we see in Iceland today with direct patronyms holding out for at least another two centuries. John son of John would not at all be an uncommon name, what with its biblical significance. Spelling of the language, and especially of names, also wouldn't be nailed down for another few centuries. Even as late as the 1600s, William Shakespeare himself spelled his own name in a whole manner of different ways.
It does lead into an interesting discussion of what names even are and how they are applied. With nothing to go on but a name, anything before around 1400 is unlikely to be related just because the name is similar sounding. At least not without being able to trace church birth/baptism records directly. And as far as I can tell we can't even go as far back as Ewan of Otter directly, despite at least three clans claiming to trace their lineage to him.
Which brings up some more interesting points of discussion. If you lot find yourself wanting to come over to this side of the pond for an event, I'd love to dive down that rabbit hole it over a few beers.