Sarah Helena (1793-1859) fourth daughter of Michael Frederick Trench (1746-1836) of Heywood, Queens Co., a cousin of Earl of Clancarty, by Anne Helena (1741-1831), daughter and heiress of Patrick Stewart of Killymoon, Co. Tyrone. Her eldest brother Major-General Sir Frederick William Trench K.C.H. M.P. (1777-1859) was Aide-de-Camp to George IV and William IV.
She married as his second wife on 7 December 1815, Sir Compton Pocklington Domville, 1st Bt. (c.1775-1857) of Templeogue and Santry House, Co. Dublin, a man who made many unsuccessful attempts to obtain a Peerage. They left issue.

Is is recorded in John Comerford's manuscripts that Lady Domville sat for her portrait in January, 1820