Alexander was descended from the Londonderry merchants Andrew Alexander and his son John (d. 1747), of Ballyclose, county Londonderry and Gunsland, county Donegal. The latter had three sons: John (d. 1766), the ancestor of the Alexanders of Milford House, county Carlow; Nathaniel (d. 1761), of Gunsland, and William (d. 1778). The youngest of Nathaniel’s three surviving sons, James, established the family’s East Indian and parliamentary fortunes, and, having represented Londonderry in the Dublin Parliament from 1775, was created successively baron (1790), viscount (1797) and earl of Caledon (1800) in the Irish peerage. His elder brother Robert, of Boom Hall, county Londonderry, was the father of Henry (1763-1818), James and Josias Du Pré Alexander, Members for Old Sarum. William, a Dublin merchant, was the father of William Alexander of Belcamp, county Dublin, lord mayor of Dublin, who was created a baronet in 1809 and whose heir Robert was a director of the Bank of Ireland. Robert Alexander, the younger brother of the 1st baronet, was a Dublin banker, who sat for Dingle, 1777-83, and Newtown, 1797-1800, in the Irish House of Commons.
Henry Alexander, Robert’s second son, had a brief career in the East India Company’s service, and thereafter operated as a private merchant in Calcutta, probably in conjunction with his relatives there. After returning to England he travelled on the continent: his father reported to the 2nd earl of Caledon, 27 Aug. 1819, that he had been ‘sporting on the Austrian mountains’, and he expressed his confidence that ‘you will like Henry ... his manners are so pleasing and unassuming, with a comportment so mild, joined to a cheerfulness that is altogether winning’.
Alexander voted against Catholic relief, 6 Mar. 1827. He divided for going into committees on the duke of Clarence’s annuity bill, 16 Mar., and the spring guns bill, 23 Mar. He presented a petition from the Protestant Dissenters of Barnstaple for repeal of the Test Acts, 15 June.
