Researching Thomas Tennison

He was born in Dillonstown, County Louth, son of Henry Tennison, Member of Parliament for Louth and grandson of Richard Tennison (1642-1705), Bishop of Meath; his mother was Anne Moore of County Fermanagh, a cousin of the Earl of Drogheda. His father was a wealthy landowner of scholarly tastes, who was part of the Dublin intellectual circle which revolved around Esther Johnson, the beloved Stella of Jonathan Swift; Henry and Swift had been friends at Trinity College, Dublin. Henry died when his son was only two years old, and Anne had died the previous year. Thomas and his sister Mary were raised by relatives, most likely by their uncle Richard Tennison junior, MP for Dunleer, who founded the County Monaghan branch of the family.

He married the heiress Dorothy Upton, daughter of Thomas Upton, Member of Parliament for Antrim, and cousin of the first Baron Templetown, by his wife Sarah Rowley of Derry. They had one son, Richard, who predeceased his father by 20 years, leaving at least one daughter but no son, so that Thomas's estate passed at his death to his nephew Dixie Coddington, the son of his sister Mary, who married Nicholas Coddington.

He went to school in Dublin and matriculated from the University of Dublin in 1725. He entered Middle Temple in 1726 and was called to the Irish Bar in 1728. He acted as a Commissioner for Revenue appeals and became Prime Serjeant in 1759. Two years later he was appointed justice of the Court of Common Pleas. He died in Dundalk in 1779, while on assize.

He represented Dunleer in the Parliament of Ireland from 1728 to 1760 and from April to December 1761. As a politician he was noted for a style of oratory which was "warm, if not always clear"; in private life he was noted as a connoisseur of wine.