Sir William Douglas, 1st of Whittinghame

Note: This profile needs primary sourcing added. A secondary source below indicates that two exist. As of late 2022, Medlands' Scotland Earls 1162-1398 mentions only one son of Sir James Douglas named William, and the mother of the one was Elizabeth Stewart, Princess of Scots. – (Ken Shelley, 22 May 2023)

Genealogics.org: Sir William Douglas, 1st of Whittinghame [1, 2]
b. Abt. 1440
d. Bef. 1484 (~ 44 years)
Father: Sir James Douglas, 1st Baron Dalkeith, d. Abt 22 May 1441 
Mother: Janet Borthwick, b. Abt 1420, d. Aft 5 Jun 1464  (Age ~ 44 years) 
Married
1. Euphemia  Married Bef 1453 
2. Margaret Fleming 

Children of 1st wife:
+ 1. Sir William Douglas, 2nd of Whittinghame, d. Aft 1527
+ 2. Katherine Douglas
Children of 2nd wife:
1. James Douglas
2. George Douglas

Sources

1. Dewar, P. B. (ed.) (2001) Burke’s Landed Gentry: The Kingdom in Scotland (including Titled and Untitled Members of the Modern Establishment). 19th ed. New York: Routledge Member of the Taylor and Francis Group. ISBN: 9781579583736. – page 296.
Notes: Two Google Books reviewers deem the source to be loaded with errata—one-star rated. Two Amazon reviews give the source a 5-Star rating without commenting why.
Problem with Source Access: There's one academic library in Scotland showing on World.cat.org as possessing Vol. 1 of this book. Broadening the scope (not including a specific volume) brings up only one other library: New Zealand. Whether this three-volume work will be meticulously emended is unknown. If it ever is reworked, it would only become available to subscribers for reading online at Burke's Peerage.

2. Johnston, G. H. (1907) “The Douglases of Morton,” in The Heraldry of the Douglases with Notes on All the Males of the Family, Descriptions of the Arms, Plates and Pedigrees. Edinburgh, Scotland, UK: W. & A. K. Johnston, p. 67 (273). Available at: Google Books, Whittinghame, nr. 273. – Note: This public domain book mentions two primary sources:– Great Seal Register (aka Registrum magni sigilli regum Scotorum) and the Privy Council Register. Locating in these sources the information found in this book would be useful.
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Clan MacFarlane Genealogy: William Douglas, 1st of Whittinghame. Note: This site provides nothing useful for proof.