Aylmer, Sir Gerald (1484?–1560), lawyer and administrator, was one of nine children of Bartholomew Aylmer of Lyons, Co. Kildare, and Margaret Aylmer (née Chevers) of Macetown, Co. Meath, a granddaughter of William Welles (qv), lord chancellor of Ireland. Though first recorded (1522) as serving the earl of Kildare, who may have secured his appointment as second justice of common pleas (1528; renewed 1532), in 1534 Aylmer was in crown service, became chief baron of exchequer, and took an active part in suppressing the Geraldine rising. He also joined the Irish council; though an important officeholder and of a major Pale family, he attended infrequently and may not have held continuous membership. As a client of Thomas Cromwell, he became chief justice of king's bench (1535), remained active in warfare and negotiations, and was knighted for his part in defeating Ó Néill and Ó Domhnaill at Bellahoe (1539). In administrative and ecclesiastical reform his allies were Sir John Alen (qv) – his partner against two lord deputies, William Skeffington (qv) and Leonard Grey (qv) – and Sir Thomas Cusack (qv). Aylmer and Cusack served together as lords justices (1552–3) on the recall of Sir James Croft (qv).
Aylmer acquired lands in Co. Meath, taken from religious houses or from the Bathe family. At Mary's accession, however, his tenure was continued and his responsibilities increased. Owing to his age he was replaced as chief justice in 1559, probably dying in late 1560. He married (c.1514) Alison FitzGerald of Alloone; they had at least two children. The Aylmers of Balrath (later ennobled) are their descendants. His sister Anne married Sir Thomas Luttrell (qv).