Grey married firstly, after 25 November 1378, Margaret de Ros, daughter of
Thomas de Ros, 4th Baron de Ros of Helmsley by Beatrice de Stafford, daughter of Ralph de Stafford, 1st Earl of Stafford, by whom he had two sons and several daughters, including: • Eleanor Grey, who married before 22 October 1397 (as his 1st wife) Robert Poynings, Knt., 4th Baron Poynings, by whom she had three sons, Sir Richard Poynings (d. 10 June 1429),
Sir Robert Poynings and Edward Poynings (d. 1484). • Thomas Grey (living 1387). •
Sir John Grey, K.G., the 2nd but eldest surviving son, (c. 1387 – 27 August 1439), who predeceased his father. He married Constance Holland, the daughter of
Elizabeth Plantagenet and
John Holland, 1st Duke of Exeter by whom he had issue, including
Edmund Grey, 1st Earl of Kent (also 4th Baron Grey de Ruthyn). • Catherine Grey (b. 1392), married George de Lucy, Baron de Lucy. •
Margaret Grey (b. c. 1397 - d. after April 1426 and before October 1427), who married
William Bonville, 1st Baron Bonville. These were the great-grandparents of wealthy heiress
Cecily Bonville, 7th Baroness Harington who married
Thomas Grey, 1st Marquess of Dorset, a descendant of Reginald Grey by his second marriage. Grey married secondly on 7 February 1415, Joan de Astley, daughter of
Sir William de Astley, 4th Baron Astley and Joan de Willoughby. Joan de Astley died in 1448. By her, he had three sons and three daughters, including: • Sir Edward Grey (c. 1415/1416 - 18 December 1457), who married Elizabeth Ferrers, 6th Baroness Ferrers of Groby, and had five children including
Sir John Grey of Groby, the first husband of
Elizabeth Woodville. • Robert Grey (born 1419), who married Eleanor Lowe. •
John Grey of Kempston,
Bedfordshire. • Constance Grey, who married
Sir John Cressy. • Elizabeth Grey, who married
Sir William Calthorpe, by whom she had issue. • Eleanor (or Alianore) Grey, who married William Lucy, esquire, of
Charlecote,
Warwickshire. • Alice Grey, married Sir John Knivett, a descendant of
Sir John Knyvett == Rebellion of Owain Glyndŵr ==