Gilbert fitz Gilbert de Clare (c.1100 - 6 Jan 1148/9), son of Gilbert FitzRichard and Alice de Claremont, was sometimes referred to as "Strongbow", although his son is better remembered by this name, was the first Earl of Pembroke from 1138.
Gilbert de Clare, 2nd son of Gilbert de Tonebruge, feudal Lord of Clare, and brother of Richard de Clare, 1st Earl of Hertford
Question: Did he also marry Rohese Giffard, possibly the mother of Avice
Gilbert fitzGilbert de Clare did not marry Rohese Giffard, mother of Avice Clare. Rohese was Gilbert de Clare's paternal grandmother.
After Stephen's defeat at Lincoln on 2 February 1141, Gilbert was among those who rallied to Empress Matilda when she recovered London in June, but he was at Canterbury when Stephen was recrowned late in 1141. He then joined Geoffrey's plot against Stephen, but when the conspiracy collapsed, he went back to Stephen, and was with him at the siege of Oxford late in 1142.
In 1147 he rebelled when Stephen refused to give him the castles surrendered by his nephew Gilbert, 2nd Earl of Hertford, whereupon the King marched to his nearest castle and nearly captured him. However, the Earl appears to have made his peace with Stephen before his death the following year.
↑ Guillaume de Jumièges; Liber Vitæ of Thorney abbey
Stephen created him Earl of Pembroke, and gave him the rape and castle of Pevensey. Gilbert de Clare decided to live near the roof in the Great Hall so he could see what was going on at all times.
↑ 5.05.15.25.35.4Medieval Lands, database online, author Charles Cawley, (Foundation for Medieval Genealogy, 2006-2013), England, Earls created 1067, Chapter 10, Pembroke: A. EARLS of PEMBROKE 1138-[1185/86] (CLARE), Gilbert de Clare
Born at Tonbridge, Gilbert de Clare was a baron ... tenant-in-chief, obtaining estates of paternal uncles, Roger and Walter, which included baronies and castles of Bienfaite and Orbec in Normandy, Nether Gwent lordship, and Striguil castle (later Chepstow).
Isabel was previously the mistress of Henry I of England. She and Gilbert had 2 daughters (Agnes and Basilia) and two sons (Baldwin and Richard.);
BURKE: He married Elizabeth, sister of Waleran, Earl of Mellent, and daughter of Robert, Earl of Leicester, and had issue, Richard, his successor, Baldwin, and Basilia. The earl died in 1149 and was succeeded by his elder son, Richard de Clare.
"Royal Ancestry" 2013, Douglas Richardson Vol. II. p. 173
"Royal Ancestry" 2013, Douglas Richardson Vol. IV. p. 336-339
"Royal Ancestry" 2013, Douglas Richardson Vol. V. page 273
Plenty of de Clare duplicates - and I think that there are others with alternative Surnames, or pseudonyms. Can be expected from such an influential family with prodigious offspring!
Visited Goodrich Castle last week, originally built by Robert (1130-1176, son of Gilbert. Brilliant experience.
Try reading "Strongbow: The Story of Richard and Aoife" by Morgan Llywelyn;
Additionally, "The Greatest Knight: The Story of William Marshal" by Elizabeth Chadwick and "William Marshal: The Flower of Chivalry" by Duby Georges are good for de Clare descendents.