So William Kneen (born IOM c1811) and Jane Rowan (born c1821) were married (Feb 1841) by the time of the 1841 census... and probably didn't have any children by June 1841. So they must be recorded as a married couple, unless for some reason they each returned to their parental homes for the Census, or he was away working, or she was, or they both were...

Trouble is I can't see them anywhere in the UK or IOM...