His paternal grandparents were Earl of Hertford Richard (The Surety) DeClare and Amica Meullent Of Gloucester; his maternal grandparents were 4th Earl of Pembroke William (The Protector) Marshall (FitzGilbert) and Isobel Fitzrichard DeClare.
1stEarl of Pembroke, EarldeClare, Abbot of Ely Gilbert FitzRichard deClare
Seigneur of Montford de Gael Ralph De Gael De Montfort
In 1215 Gilbert and his father were two of the barons made Magna Carta sureties and championed Louis "le Dauphin" of France in the First Barons' War, fighting at Lincoln under the baronial banner.
His widow Isabel later married Richard Plantagenet, Earl of Cornwall and King of the Romans.
1200, Tewkesbury, Gloucestershire, daughter of Sir William Marshal, Earl of Pembroke, Mareschal of England, and Isabel deClare.
Gilbert fitz GilbertdeClare was high in the favor of Henry I, perhaps because his wife Isabell, daughter of Robert de Beaumont, Count of Meulan and Earl of Leicester, was one of Henry's favourite mistresses.
GilbertdeCLARE assumed the title of Earl of Gloucester and Hertford and was charged £350 relief for the honors of Clare, Gloucester, St. Hilary and his half of the old Giffard barony.
EarlGilbert's other daughter, Isabel born 1226, married 1240 the Scots baron Robert Bruce, lord of Annandale (d 1295), and by him was the grandmother of the hero of Bannockburn.
In 1253 his ten-year-old son Gilbert, called the Red because of the color of his hair, was married to Alice of Angouleme, daughter of Guy de Lusignan and therefore a stepniece of the King.
The Earl ofGloucester took this alliance with royalty seriously, but as he was intensely proud and most tenacious of his rights as a leading peer,Henry had never been able to count on his support.
In the course of an angry discussion the latter charged that the earl was in league with the Welsh because the lands of Gloucester had been spared in thelast raids.
