I think I have resolved what I thought was an"an o'maly".
The transcriptions for the 1828 marriage of Esther Sutherland to Alexander Broadfoot(St. Marylebone) has both parties aged 21.This initially led me to believe it was Esther,DAUGHTER of Captain John Sutherland,baptised 1811 in Rathkeale.However,the 1841 census with a Jessie Sutherland present,found by MonicaL,suggests she is a generation older.Given Alexander dying in 1837 aged 57,the transcription probably means "at least 21/of full age" and Esther is actually the SISTER of Capt.John Sutherland,as per the WikiTree,as therefore ,also,is that Jessie.
This is consistent with the WikiTree I referred to.It should be noted that Helen Sutherland also marries a Broadfoot(William) in 1800 on Orkney(home to Captain John's father James,Lord Duffus).
Regards,
Rogrer