Nielsen Hayden genealogy
Family: Robert de Willoughby / Margaret Deincourt (F8567)
m. Bef 1304-
Male
Robert de Willoughby
Birth Between 1250 and 1260 Death Bef 25 Mar 1317 Burial Marriage Bef 1304 [1] Father William de Willoughby | F8568 Group Sheet Mother Alice Beke | F8568 Group Sheet
Female
Margaret Deincourt
Birth Death Bef 18 Oct 1333 Burial Father Edmund Deincourt | F3039 Group Sheet Mother
Male
+ John de Willoughby
Birth 6 Jan 1304 Death 13 Jun 1349 Burial Spilsby, Lincolnshire, England 
Spouse Joan Roscelyn | F8565 Marriage Bef 2 Jul 1323
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Sources - [S128] The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Extant, Extinct or Dormant ed. Vicary Gibbs, H. A. Doubleday, Duncan Warrand, Howard de Walden, Geoffrey H. White and R. S. Lea. 2nd edition. 14 volumes (1-13, but volume 12 spanned two books), London, The St. Catherine Press, 1910-1959. Volume 14, "Addenda & Corrigenda," ed. Peter W. Hammond, Gloucestershire, Sutton Publishing, 1998.
- [S128] The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Extant, Extinct or Dormant ed. Vicary Gibbs, H. A. Doubleday, Duncan Warrand, Howard de Walden, Geoffrey H. White and R. S. Lea. 2nd edition. 14 volumes (1-13, but volume 12 spanned two books), London, The St. Catherine Press, 1910-1959. Volume 14, "Addenda & Corrigenda," ed. Peter W. Hammond, Gloucestershire, Sutton Publishing, 1998.