I think this is an error in the book.
Memorials of Old Derbyshire edited by John Charles Cox
http://books.google.com/books?id=c8hCAAAAYAAJ&pg=PA103-IA2&...
Pg.100
Seems to state that John Foljambe, of Tideswell and Wormhill was the son of (Sir Thomas Foljambe, III, Kt., of Tideswell and Wormhill, etc. Sir Thomas III who died in 1323 who would of married Alice Furnival, (the son of Sir Thomas Foljambe, II, Kt., of Tideswell, Wormhill, Elton and Katherine le Eyr)), and that he had a younger brother Thomas who had sons John & Thomas of Elton both of who died childless. Yet Sir Thomas III who died in 1323 does not have a son John who was living in 1350. Then on Pg.101 it list the four generations of Thomas' with the wives and dates of deaths of the 1st three, listing a John (d.1358) son of Thomas IV & Aveline (his first wife) who would be half brother of Godfrey.
I think the statement on Pg.100 about John Foljambe, of Tideswell and Wormhill John's father dying in 1323 is an error (saying also the last named Thomas) who would of been Sir Thomas Foljambe, IV, Kt., of Tideswell and Wormhill Thomas the fourth who's date of death is not listed.
I think the children listed are correct, but I could find no information on unknown wife of Rychert Donham sister of Sir Thomas Foljambe, IV, Kt., of Tideswell and Wormhill