Per IGI a John Colvin md a Sarah Greggor 9 Oct 1880 German
a Sarah Greggor was mother of a George William Greggor, no father listed ch 10 Apr 1874 German

There are 3 Sarah Greggors in German in the 1840's
One of then has a father named George Greggor & a brother George William Greggor.

Not much help, just adding to the confusion