Martin CALLOW b.1839 is likely to be of the CALLOW "Plun", Maughold, line as described on pg 331 of the Radcliiffe's "History of Kirk Maughold [1979 Manx Heritage Trust]

There is discussion on this line at the CALLOW Forum

http://genforum.genealogy.com/callow/

John CALLOW 1886-1960 "The Maughold Giant" and Griffith CALLOW are also descendants.

See also

http://www.my-ged.com/callow

although it appears from Sheena's message that the SHEERAN connection is inaccurate.

Any further information on this line would be welcomed by Sheena and myself