Elaine, your Edward Corteen clue was a good one. When I was unable to work out how Edward's grandmother could have been a Christian, I wrote to Philip Allen who knew him well, and also has a very good collection of Constance Radcliffe's work.

Philip replied that in his letter Edward Corteen was almost right, but had missed a generation. Miss [Isabella] Christian, Baldromma was his great-grandmother. Edward had an amazing knowledge of IOM family relationships, and all done not by studying parish registers, but by taking an interest in what people said.

Philip kindly checked one of Constance Radcliffe's charts (for The Flatt), and wrote:
Caroline Jane Lucy Christian (b Le Havre 1883, d Ramsey 1944) was the daughter of Howard Christian and Marie Lebaille
Howard Christian (b & d in France) was the son of Robert Oates Christian and Jane Sayle
Robert Oates Christian (merchant of Le Havre and first Chairman of Ramsey Tow Commissioners, b 1795, d 1867) was the son of John Christian and Catherine Oates (1774-1841).
John Christian (Captain in the Royal Manx Fencibles who sold most of the Flatt, d 1837) was the son of John Christian, the Flatt (1728-1773) and Catherine Callow.
Catherine Callow (b 1745) was the daughter of Edward Callow, Ballaglass (1709-1753) and Anne Callow, Claughbane (d 1775).
These two had another daughter Dorothy Callow (1742-1832) who married Robert Christian, Baldromma (1743-1820).
Their son Edward Christian, Baldromma (1773-1852) married Isabella Kermeen, Ballig (1796-1867, granddaughter of Philip's g-g-g-g-grandparents Daniel Joughin, Rhenabb and Isabella Kerruish, Booilevelt).
Their daughter Isabella ("Miss Christian") Christian (1829-1899) married Robert Kerruish, Ballafayle (1830-1902).
Their daughter Catherine Ann Kerruish (1858-1951) married James Callow, Ballaskeig (1853-1924).
Their daughter Ellen Elizabeth Callow (1876-1958) married James Alfred Corteen (1870-1954, of the Ballasholague line)
They were the parents of Edward Corteen (1901-1990).
[Who was also a very distant relative of mine through the Ballasholague line.]

So Caroline was the fourth cousin of Edward's mother.

If you are not a member of the IoMFHS I suggest you join. They would have a copy of CR's sketch chart about Christian from The Flatt which would have all the relationships previously mentioned, and the ones from her books. If you are a member they would copy and post this to you just for photocopying and postage costs.

Sue