Aylmer, Sir Gerald (d. 1634), 1st baronet, landowner, was third son of Richard Aylmer of Lyons, Co. Kildare, and his wife Elinor, daughter of George Fleming. By 1582 he had travelled to London in pursuit of property claims, carrying commendations of his conduct during the recent Baltinglass rebellion, but he soon emerged as a leading figure in the Pale-based campaign against government exactions (‘cess’); by 1583 efforts were underway to gather funds in Co. Meath to support him as ‘their solicitor . . . for redress of the intolerable charge of cess’ (CSPI, 1574–85, 438). Aylmer remained part of the ‘organising core of the country opposition’ in the 1580s (Brady, 240). By 1588, when he returned to London, he had married Mary, widow of James Eustace, 3rd Viscount Baltinglass (qv), and daughter of Henry and Jane Travers. On this occasion he suffered imprisonment but, on his release, was admitted to Gray's Inn (as ‘Garrett Aylmer’), by Lord Burghley, 26 February 1589, while he and his wife in 1589–90 secured further grants of property.
In 1591 he was one of those upon whom the Dublin government imposed a bond to attend worship in the established church; his bond forfeited he travelled to London to protest but was imprisoned again, this time for fourteen months, securing his release in August 1592 with an oath of loyalty to Elizabeth and, it would seem, some indication of religious conformity. Aylmer was knighted (17 June 1598). His possessions lay mostly in the counties of the Pale, his principal residence by the late 1590s being Donadea castle, Co. Kildare, which he rebuilt (1624). He was involved in the renewal of composition in lieu of cess in 1605, once again being sent to England as part of an agency from the Pale. By the end of the year a renewed drive to press religious conformity saw him among the signatories of a petition seeking to postpone proceedings. By 1608 he may have joined in carrying the protest to London, perhaps facing prison once more. Following the death of his wife, on 28 November 1610, in 1612 he re-married, his second wife being Julia Nugent (d. 1617), daughter of Christopher Nugent (qv), Lord Delvin, and his wife Mary; there was one son and at least one daughter by this marriage. He was made a baronet (privy seal 10 December 1621, patent 25 January 1622) and died 19 August 1634. He was buried at Donadea.