seems strange that he 'settled' next door to an unrelated family of the same name ? - though as you know cubbon/cubbin is quite common in Arbory but I think these were the only two families cheek by jowl.
It would be worthwhile checking out the Kewley connection - people didn't move around as much (ag labs couldn't afford horses, roads were poor, thus you tended to court someone within relatively easy reach - likewise they had to meet and an age gap of 5 years with him being quite young at marriage looks to me as though some matchmaking went on - is he entered for any land in the manorial roll ?.