Another anon, still bugging you about Bronze Yohn. Do you think the shared culture bond between the Starks and the Royces could account for the proximity, or at least played a part in the forging of those bonds generations past?

Definitely the latter. If you look at the Stark family tree, they almost entirely either marry within the North or to houses outside the North that are First Men in origin. So when the Starks were looking for a bride for Beron, the First Men heritage of the Royces and the way in which the Royces have preserved that heritage (although not their religion, interestingly), definitely helped.