John, I don't have much, but Humphrey is mentioned in Burke's Genealogical and Heraldic History of the Peerage, Baronetage and Knightage, 1921, page 58:
"Lineage - The lands of Abercromby, in Fife, gave name to a family of Abercromby of that ilk, whose direct line ended in the 17th century, and since then the Abercrombys of Birkenbog, co. Banff, have considered themselves the chief family of the name. The ancestors of the latter were, in the 14th century, possessors of Pitmedden, Ardune, Harthill, &c., in Aberdeenshire. A charter by Thomas, Earl of Mar, confirmed to Alexander Abercromby, a grant by the Bishop of Aberdeen, of the lands of the park of Galcross (now called Birkenbog), Aberdeen, 1 Nov. 1362.Humphrey Abercromby, of Pitmedden (1457) was s. by his son, Alexander (1488), father of another Alexander, who had sasine of Pitmedden 26 Aug. 1484. This ALEXANDER ABERCROMBY, of Pitmedden, m. Marjory Mowat, and had issue,"
(Note: The "s." means "succeeded")
"Burke's Genealogical and Heraldic History of the Peerage, Baronetage and Knightage" is one of the references held in high regard.I found a copy in the Fairfax, Virginia library in the Virginia Room (genealogy section), but it was located in the "rare books" section.
I have been doing a great deal of research on the Abercrombie's in Scotland because I have been having trouble connecting them to the Abercrombies in S.C. (James Abercrombie who was the Attorney General in S.C. is NOT the link.That James Abercrombie never married and had no children).