Thomas Dillon, 4th Viscount Dillon

Thomas was born in March 1615^[b] in Ireland. He was the second son of Christopher Dillon and his wife Jane Dillon. His father was the eldest son and heir apparent of Theobald Dillon, 1st Viscount Dillon. Christopher predeceased his father and therefore never succeeded as viscount. He was a member of the landed gentry and known as Christopher Dillon of Ballylaghan in County Mayo.

Thomas's mother was the eldest daughter of James Dillon, 1st Earl of Roscommon. His father's and his mother's family were branches of the same widespread Old English family, established in Ireland in 1185 when Sir Henry Dillon accompanied Prince John to Ireland.^[5] His parents married in 1604 and had seven sons and five daughters.^[6]

His father died on 28 February 1624 when Thomas was eight years old.^[15] His grandfather, the 1st Viscount, followed him into the grave two weeks later on 15 March 1624.^[16] His elder brother Lucas succeeded his grandfather as the 2nd Viscount Dillon. This Lucas stayed viscount for about five years and died in 1629,^[17] leaving a three months old child, Theobald,^[18] who became the 3rd Viscount and a ward of the King but lasted only about a year dying on 13 May 1630 in his infancy.^[19] Thomas, being his uncle, succeeded as the 4th Viscount Dillon of Costello-Gallen. As he was 15 at the time, he became a ward and the estate was seized by the King, who sold the wardship to Thomas's uncle Lucas Dillon of Loughglynn.^[20] (see Family tree) and to Charles Wilmot, 1st Viscount Wilmot.^[21] Lord Dillon, as he was now, in that same year converted to Protestantism and was received into the Church of Ireland.^[22]

In 1635 Lord Dillon, aged about 20, married Frances White, daughter of Nicholas White, esquire, of Leixlip, a Protestant,^[23][24] and granddaughter of Garret Moore, 1st Viscount Moore by her mother Ursula Moore.^[25] She brought him a dowry of £3000 (about £600,000 in 2023^[26]). Her sister Mary married Theobald Taaffe, the 2nd Viscount Taaffe (later 1st Earl of Carlingford), who thus became his brother-in-law.^[27]

Lucas and Frances had six sons and several daughters, who seem not to be known by name. The sons were:

1. Charles (born 1636), became a general in French and Spanish service;^[28]
2. Christopher (died 1663), never married;^[29]
3. Rupert, died while being a page to Charles II, during his exile;^[30]
4. Thomas (died 1674), became the 5th Viscount;^[31][32]
5. Ormond, died young;^[33]
6. Nicholas, died young.^[33]

Thomas Wentworth, Viscount Wentworth, later the 1st Earl of Strafford, was appointed Lord Deputy of Ireland by Charles I on 12 April 1632.^[34] About 1636 Wentworth's sister Elizabeth married James Dillon, 3rd Earl of Roscommon, a first cousin on his mother's side.^[35] In January 1640 Wentworth was raised to Lord Lieutenant of Ireland.^[36] On 12 January 1640 Wentworth was created 1st Earl of Strafford.^[37]

Lord Strafford, as he now was, summoned an Irish Parliament in 1640. This was the second Irish parliament of King Charles I. On 16 March of that year, Lord Dillon took his seat in the House of Lords,^[38] which comprised all Irish peers and had a Catholic majority. The purpose of the parliament was to raise subsidies for an Irish army of 9000^[39] for Charles I to fight the Scots in the Bishops' Wars. The Parliament unanimously voted four subsidies of £45,000.^[40] On 31 March 1640 parliament was prorogued until the first week of June.^[41][42]

On 3 April 1640 Strafford left Ireland,^[43] called elsewhere by the King, having appointed Christopher Wandesford as Lord Deputy.^[c] Wandesford opened the second parliamentary session on 1 June 1640.^[45][46] News from England was that the Short Parliament had refused subsidies to the King.^[47] The Irish MPs regretted having voted for subsidies and wanted to change how they would be evaluated and collected.^[48] After two weeks of inconclusive discussions, Wandesford prorogued parliament on 17 June.^[49]

When Parliament met again on 1 October, its mood had turned entirely against Strafford. The Commons sent a committee to England with a remonstrance that listed Strafford's excesses. Dillon together with Gormanston, Kilmallock and Muskerry were sent to London by the House of Lords to report grievances.^[50] Sometime in 1640 before the 23 October Lord Dillon was appointed a member of the Irish Privy council.^[51] Wandesford died on 3 December 1640 and was succeeded by Lord Leicester with the title of Lord Lieutenant of Ireland. Lord Leicester, however, never set foot on Irish soil.^[52]