From History of Allegheny County, Pennsylvania:
David Duff, farmer, postoffice Emsworth, was born in this county, April 1, 1849.David Duff married Miss Mary M., daughter of Thomas D. Hamilton, and four children have blessed them: James S., Olive B., Harry L. L. and Pearl A.
From Memoirs of Allegheny County, Pennsylvania:
David Duff was married to Mary Hamilton, Jan. 13, 1873, and to them were born six children, James S., Olive B., Harry L., Pearl A., Margaret E. and Elmer I. David Duff succeeded his father as justice of the peace in Ohio township, which office he held at the time of his death, Aug. 14, 1897.
Have you taken a DNA test? If so, login to add it. If not, see our friends at Ancestry DNA.