Henry was born in February 1692,[2] the third and youngest son of Gustavus Hamilton and his wife Elizabeth Brooke. His father would in 1715 be ennobled as Baron Stackallan and in 1717 advanced to Viscount Boyne.[3][4]
In the Irish election of 1715 the Henry Hamilton was elected as one of the two members of parliament (MPs) for St Johnstown Borough in the House of Commons of the only Irish Parliament of King George I.[7] He held that seat during the entire duration of the parliament from 12 November 1715 to 11 June 1727 when it was dissolved by the king's death.
Hamilton did not contest the Irish election of 1727, which was held for the only Parliament of King George II, which lasted from 14 November 1727 to 25 October 1760. However, in 1730 he contested and won the by-election for one of the two seats for County Donegal that resulted from the death of Alexander Montgomery on 19 December 1729.[13] Hamilton sat for this county until his death in 1743 when he was replaced by Andrew Knox.[14] His father and his two older brothers Frederick and Gustavus had also represented County Donegal in the House of Commons.
^Cokayne 1910, p. 4. "Tabular pedigree of the Earls of Abercorn"
^ abBurke & Burke 1915, p. 289, right column, line 30. "3. Henry, MP for Donegal, and collector for the port of Cork, b. [born] Feb. 1692; m. [married] 27 Oct 1722 Mary, eldest dau. [daughter] of Joshua Dawson ..."
^ abcCokayne 1912, p. 266, line 34. "He was on 20 October 1715, cr. [created] Baron Hamilton of Stackallan [I. [Ireland] ]."
^Cokayne 1912, p. 266, line 35. "... was cr. [created] on 20 Aug. 1717, Viscount Boyne in the province of Leinster [I. [Ireland] ]."
^Debrett 1828, p. 765 line 26. "... m. [married] Elizabeth, da. [daughter] of Sir Henry Brooke, of Brooke's Borough, co. Fermanagh, knt., and by her had issue ..."
^Lodge 1789, p. 178, line 3. "He [Gustavus] married Elizabeth, second daughter of Sir Henry Brooke of Brooke's Borough in the county of Fermanagh, Knt. ..."
^Burke & Burke 1915, p. 289, right column, column, line 30. "3. Henry, MP for Donegal, and collector for the port of Cork, b. [born] Feb. 1692; m. [married] 27 Oct 1722 Mary, eldest dau. [daughter] of Joshua Dawson ..."
^Lodge 1789, p. 178, line 23. "In October 1722 he married Mary, eldest daughter of Joshua Dawson of Castle-Dawson in the county of Derry."