William Trench, 3rd Earl of Clancarty
William Thomas Le Poer Trench, 3rd Earl of Clancarty, 2nd Marquess of Heusden (21 September 1803 – 26 April 1872), styled Viscount Dunlo between 1805 and 1837, was an Irish peer, as well a nobleman in the Dutch nobility.
He was educated at St John's College, Cambridge.
Trench was born in Castleton, County Kildare, Ireland the son of Richard Trench, 2nd Earl of Clancarty and Henrietta Margaret Staples.
On 8 September 1832, he married Lady Sarah Juliana Butler.
They had six children.
Power Le Poer Trench
Power Le Poer Trench DD( 1770 – 1839) was an Anglican clergyman who served in the Church of Ireland as firstly Bishop of Waterford and Lismore, then Bishop of Elphin and finally Archbishop of Tuam.
Brinsley Le Poer Trench, 8th Earl of Clancarty
William Francis Brinsley Le Poer Trench, 8th Earl of Clancarty, 7th Marquess of Heusden( 18 September 191118 May 1995) was a prominent ufologist.
He was an Irish peer, as well as a nobleman in the Dutch nobility.
John Mackay (poet)
John Mackay( 1656–1754), known as( The Blind Piper), was a Scottish Gaelic poet and composer, and the grandfather of William Ross.
William Le Poer Trench
Colonel The Hon.
William Le Poer Trench CVO, JP (17 June 1837 – 16 September 1920) was an Anglo-Irish politician and British army officer.
He was the third son of William Trench, 3rd Earl of Clancarty and Lady Sarah Juliana Butler.
He married Harriet Maria Georgina Martins, daughter of Sir William Martins, on 21 April 1864.
He fought in the Second Opium War between 1857 and 1858, commanding a ladder company at the capture of Guangzhou and Nankow, and was mentioned in despatches.
He gained the rank of Colonel in the service of the Royal Engineers.
Between 1872 and 1874, he was Member of Parliament (MP) for County Galway, having unseated the elected MP, John Philip Nolan, on petition; the case was one of the most controversial Irish cases of its time and permanently damaged the reputation of the judge, William Keogh.
He held the office of Justice of the Peace for Westminster, London, Buckinghamshire, and Middlesex.
He was made a Commander of the Royal Victorian Order in 1912.
Power Henry Le Poer Trench
Power Henry Le Poer Trench( 11 May 1841 – 30 April 1899) was a British diplomat.
Trench was the son of William Thomas Le Poer Trench, 3rd Earl of Clancarty and Lady Sarah Juliana Butler.
William Le Poer Trench (Royal Navy officer)
Rear- Admiral The Hon. William Le Poer Trench( 4 July 1771 – 14 August 1846) was born in Garbally, Galway, Ireland to William Power Keating Trench, 1st Earl of Clancarty and Anne Gardiner.
He acted for a considerable period as the agent of the estates of his father's family in Ireland.
He was made a Lieutenant in the Royal Navy in 1793; promoted to the rank of Commander in 1799; to that of Post Captain 1802; and to that of Rear Admiral in 1840.
In 1819 he was appointed Secretary to the Board of Customs and Port Duties in Ireland.
Richard Trench, 2nd Earl of Clancarty
Richard Le Poer Trench, 2nd Earl of Clancarty, 1st Marquess of Heusden (19 May 1767 – 24 November 1837), styled The Honourable from 1797 to 1803 and then Viscount Dunlo to 1805, was an Irish peer, a nobleman in the Dutch nobility, and a diplomat.
He was an Irish, and later British, Member of Parliament and a supporter of Pitt.
Additionally he was appointed Postmaster General of Ireland, and later, of the United Kingdom.
Robert Le Poer Trench
Robert Le Poer Trench( c.1811 – 8 February 1895) was a judge and an Attorney- General of Victoria.
Trench was the third son of Ven. Charles Le Poer Trench, D.D., of Ballinasloe, County Galway, Archdeacon of Ardagh, and grandson of the first Earl of Clancarty.
He entered as a student of the Middle Temple in May 1839, and was called to the Bar in June 1842.
Having emigrated to Victoria, he was clerk of petty sessions at Kilmore, Victoria and afterwards at Ballarat.
In 1855 he was admitted to the Victorian Bar, and quickly obtained a large practice, especially in mining cases.
Though he never entered parliament he was Attorney- General in the first Graham Berry Government from August to October 1875, and in Berry's second Administration, from May 1877 to March 1878, when he was appointed a Commissioner of Land Tax, and a County Court Judge in April 1880.
Mr. Trench, who was appointed Q.C. in 1878, subsequently retired on a pension.
Nicholas Trench, 9th Earl of Clancarty
Nicholas Le Poer Trench, 9th Earl of Clancarty, 8th Marquess of Heusden( born 1 May 1952), is an Anglo- Irish peer, as well as a nobleman in the Dutch nobility.
Lord Clancarty serves as an elected Crossbench hereditary peer in the British House of Lords.
His earldom is in the Peerage of Ireland.
He was educated at Westminster School.

Question: Who is William Le Poer Trench's paternal grandfather?