The Complete Peerage names him as younger brother of Roger de Quincy Earl of Winchester but does not cite the corresponding source. The primary source which confirms his parentage has not yet been identified. He is named “Roberto [de Quinci]” in the Annals of Dunstable when recording his marriage. His birth date range is suggested on the assumption that he was born after the death of his older brother also called Robert.... 1
11 Jan 1251, Westminster
The king has pardoned to Robert de Quincy 20 m. of the 60 m. at which he was amerced before the justices last itinerant to take the pleas of the forest in Nottinghamshire, and has granted him that he may render 10 m. annually of the [remaining] 40 m., namely 5 m. at the Exchequer of Easter in the thirty-fifth year, 5 m. at the Exchequer of Michaelmas next following, and 10 m. thus from year to year at the same terms until the aforesaid 40 m. are paid to the king. Order to the barons of the Exchequer to cause Robert to be quit from the aforesaid 20 m., to have the same terms for the remaining 40 m., and to cause this to be done and enrolled thus.
Calendar of Fine Rolls, 35 Hen. III, 175
9 Nov 1264, St. Paul’s, London
To Richard de Hemington’ and Richard de Wikes, keepers of the lands formerly of R. de Quincy, sometime earl of Winchester. Because the king has heard by the inquisition that he caused to be taken by them that Robert de Quincy, some time before his death, had granted the manor of Stivinton with appurtenances by his charter to Roger de Quincy, formerly earl of Winchester, to have to the same earl and his legitimate male heirs of his body, namely so that if it were to happen that the said earl were to die without legitimate male heirs of his body the aforesaid manor would revert to Robert or to his heirs, and that Joan, wife of Humphrey de Bohun junior, and Hawise, her sister, are the daughters and heiresses of the aforesaid Robert, and that the aforesaid manor ought to revert to them as to the legitimate heirs of the same Robert, and that the abovesaid Joan is of full age, the king, wishing to do special grace to the abovesaid Humphrey and his aforesaid wife, commands them that, once the dower falling to her from the aforesaid manor has been assigned to the countess of Winchester, and once the partition of the remainder of the aforesaid manor has been undertaken between the abovesaid Joan and Hawise, they are to cause the same Humphrey and Joan to have full seisin of the share falling to them, saving to the abovesaid Humphrey and Joan the first born the capital messuage of the same manor, together with all things taken therefrom from the time of the seizure of the same manor into the king’s hand, for the abovesaid Humphrey has found the king pledges, namely Giles de Argentan and Walter of Crepping, to perform his homage to the king and to render his relief to him for his aforesaid share if that homage and relief ought to pertain to the king, provided that they retain the share falling to the abovesaid Hawise, who is underage and in the king’s custody, in the king’s hand, so that they might answer the king for the issues of the same at the Exchequer.
Calendar of Fine Rolls, 49 Hen. III, 28