Going back to the early "Kildare" history William Adare in 1599 said he was of Kildare).
c.1200 Strongbow, Earl of Pembroke, m. EVA, heiress of Palatinate of Leinster. Strongbow's son-in-law, Richard Marshall, Earl of Pembroke, was killed aided by Fitzgeralds. Richard Marshall's grandaughter, Agnes, m. Wm. de Vescy who lost the property shortly after in consequence of his fleeing into France to avoid a single combat with John Fitzgerald who had charged him with treason, and de Vescy's possessions were bestowed on John FitzGerald, his accuser.
1294 Callhach O'Connor of Offaly took the town and Castle of Kildare and destroyed the Rolls.in "Calendar of Documents relating to Scotland" vol.II 1272-1307 p.105 July 1290 #444extract: William de Vescy declares that he promised Alianora Queen of England, that John de Vescy his son should endow his wife Clemencia, her cousin with a dower, but being absent on the King's (Ed.I. of England) affairs, she shall have dower from their entire heritage in addition.
16th Oct. 1295, Calander of Patent Rolls. 1292-1301, #154. de Vescy went to France for his health. (to save his head)
22nd June 1297. As William de Vescy (Fitzgerald?) has granted to him (King Ed.I of England) the castle, manor and co. of Kyldare in Ireland, and also the manor of Sprouston with pertinents both in England and Scotland, whereof Clemencia widow of John de Vescy his son has 2/3 , Isabella widow of John de Vescy, William's brother, has 1/3 in dower, the King grants Kyldare to William for his life and also Sprouston after the death of Clemencia and Isabella all revert to the King and his heirs after the death of William.William died soon after.
Would it have been this feud of the FitzGeralds which led to the duel of the Adair's ancestor with the White Knight ?
If the White Knight's title then went to Mr. King who became the Earl of Kingston (did he marry Margaret Fitzgerald?) then it may help to trace her ancestors to confirm the date of the duel for the confirmation of the history of FitzGerald-Adair name.