In Domesday Survey occurs the name of Walter Fitz-Other, Castellan of Windsor and Warden of the Forests in Berkshire, being then possessed of two lordships in Berkshire, three in Surrey, three in Bucks, three in Dorsetshire, four in Middlesex, nine in Wiltshire, one in Somerset, and ten in Hampshire, all of which Dominus Otherus, his father, held in the time of King Edward the Confessor. Walter was treated as a fellow-countryman by the Normans after the Conquest. He married a daughter of the Prince of North Wales, and had three sons, the eldest of whom, Gerald, assumed, according to the custom of that day with eldest sons, the name Fitz-Walter.34

From "Complete Peerage England, Scotland, Ireland, Great Britian" by George E Cokayne, CS421.G2 1982, v X, page 10, Offaly (a):
Walter FitzOther of Windsor (b) a Domesday tenant of lands in Berkshire, Bucks, Middlesex, Hants and Surrey, held a barony owing 15 or 20 knights' fees to the castle guard of Windsor, where he was Keeper of the Great Forest and castellan of the castle. He married Beatrice. He was living in or after 1100 (c).
(a) The feudal barony of Offaly never became a peerage in the modern sense but as the ancestors of the Earls of Kildare who held it were styled barons of Offaly it is convenient to enumerate them under that designation.
(b) For J. H. Round's discoveries as to his sons, including Gerald, whose parentage was theretofore unknown, see Ancestor, no. 1, p. 122 et. seq.,no. 2, p. 91 et. seq.
(c) Idem, no. 1, pp. 122-24.