Isabel Marshal
Isabel Marshal (9 October 1200 – 17 January 1240) was a medieval English countess.
She was the wife of both Gilbert de Clare, 4th Earl of Hertford and 5th Earl of Gloucester and Richard, 1st Earl of Cornwall (son of King John of England).
With the former, she was a great grandmother of King Robert the Bruce of Scotland.
Maud de Lacy, Countess of Hertford and Gloucester
Maud de Lacy,( 25 January 1223 – 10 March 1289), was an English noblewoman, being the eldest child of John de Lacy, 2nd Earl of Lincoln, and the wife of Richard de Clare, 5th Earl of Hertford, 6th Earl of Gloucester.
Bogo de Clare
Bogo de Clare (21 July 1248 – October 1294) was a member of the Anglo-Norman de Clare family, as third son of Richard de Clare (1222–1262), 5th Earl of Hertford and 6th Earl of Gloucester.
Isabella of Gloucester and Hertford
Isabella de Clare( 2 November 1226 – 10 July 1264) was the daughter of Gilbert de Clare, 4th Earl of Hertford and 5th Earl of Gloucester and Isabel Marshal.
She is also known as" Isabel de Clare", but this is however, the name of many women in her family.
Thomas de Clare, Lord of Thomond
Thomas de Clare, 1st Lord of Thomond, 1st Lord of Inchiquin and Youghal( 1244×124729 August 1287) was a Hiberno- Norman peer and soldier.
He was the second son of Richard de Clare, 6th Earl of Gloucester and his wife Maud de Lacy, Countess of Gloucester.
In 1272 he served a term as Lieutenant of the Duchy of Aquitaine.
On 26 January 1276 he was granted the Lordship of Thomond by Edward I of England; he spent the next eight years attempting to conquer it from the O'Brien dynasty, kings of Thomond.
Gilbert de Clare, 7th Earl of Gloucester
Gilbert de Clare, 6th Earl of Hertford, 7th Earl of Gloucester, 3rd Lord of Glamorgan, 9th Lord of Clare( 2 September 1243 – 7 December 1295) was a powerful English noble.
He was also known as" Red" Gilbert de Clare or" The Red Earl", probably because of his hair colour or fiery temper in battle.
He held the Lordship of Glamorgan which was one of the most powerful and wealthy of the Welsh Marcher Lordships as well as over 200 English manors( 172 in the Honor of Clare).
Richard de Clare, 6th Earl of Gloucester
Richard de Clare, 5th Earl of Hertford, 6th Earl of Gloucester, 2nd Lord of Glamorgan, 8th Lord of Clare (4 August 1222 – 14 July 1262) was son of Gilbert de Clare, 4th Earl of Hertford and Isabel Marshal.
He was also a powerful Marcher Lord in Wales and inherited the Lordship of Glamorgan upon the death of his father.
He played a prominent role in the constitutional crisis of 1258–1263.
Margaret de Clare
Margaret de Clare, Countess of Gloucester, Countess of Cornwall( 12 October 1293 – 9 April 1342) was an English noblewoman, heiress, and the second- eldest of the three daughters of Gilbert de Clare, 6th Earl of Hertford and his wife Joan of Acre, making her a granddaughter of King Edward I of England.
Her two husbands were Piers Gaveston and Hugh de Audley, 1st Earl of Gloucester.
Eleanor de Clare
Eleanor de Clare, suo jure 6th Lady of Glamorgan( 3 October 1292- 30 June 1337) was a powerful English noblewoman who married Hugh Despenser the Younger and was a granddaughter of Edward I of England.
With her sisters, Elizabeth de Clare and Margaret de Clare, she inherited her father's estates after the death of her brother, Gilbert de Clare, 8th Earl of Gloucester, 7th Earl of Hereford at the Battle of Bannockburn in 1314.
She was born in 1292 at Caerphilly Castle in Glamorgan, Wales and was the eldest daughter of Gilbert de Clare, 6th Earl of Hertford, 7th Earl of Gloucester, 5th Lord of Glamorgan and Princess Joan of Acre.
Gilbert de Clare, 5th Earl of Gloucester
Gilbert de Clare, 4th Earl of Hertford, 5th Earl of Gloucester, 1st Lord of Glamorgan, 7th Lord of Clare( 1180 – 25 October 1230) was the son of Richard de Clare, 3rd Earl of Hertford( c. 1153 – 1217), from whom he inherited the Clare estates.
He also inherited from his mother, Amice Fitz William, the estates of Gloucester and the honour of St. Hilary, and from Rohese, an ancestor, the moiety of the Giffard estates.
In June 1202, he was entrusted with the lands of Harfleur and Montrevillers.

Question: When is Richard De Clare, 6Th Earl Of Gloucester's mother's birthday?