William Scot

William Scot is not known to have been a son of John de Balliol I, 5th Baron of Bywell and Dervorgilla of Galloway, Lady Balliol

This is a specialty site on medieval genealogy.

http://fmg.ac/Projects/MedLands/SCOTLAND.htm

extracting from it:

JOHN de Balliol, son of HUGH Balliol of Barnard Castle & his wife Cecilie de Fontaines (-before 27 Oct 1268).

m (1233[845]) DEVORGUILLA of Galloway, daughter of ALAN Lord of Galloway & his second wife Margaret of Scotland (-28 Jan 1290, bur Sweetheart Abbey, Kirkland).

John & his wife had children:

• 1. HUGH Balliol (Barnard Castle [1237/40]-[Palestine] before 10 Apr 1271)
• 2. ALAN Balliol (-[1271/78]).
• 3. ALEXANDER Balliol (-before 13 Nov 1278).
• 4. JOHN Balliol ([1250]-in France [either Château Gaillard, Normandy or Bailleut-en-Gouffern, Normandy] [4 Mar 1314/4 Jan 1315], bur [Church of St Waast, Normandy]). The Annales Londonienses name "Johan de Baillol" as son of "la secunde fille Aleyne, Devergoille"[870]. He succeeded his brother in [1278] as Lord of Bywell, co. Northumberland and Barnard's Castle, co. Durham. He succeeded in 1292 as JOHN King of Scotland.
• 5. CECILY Balliol (-[before 10 Apr 1273]).
• 6. ADA Balliol (-after 27 Dec 1283).
• 7. ALIANORE [Mary/Marjory] Balliol .