Lady Helen Laura McDonnell was the daughter of Hugh Seymour McDonnell, 4th Earl of Antrim, and Lady Laura Cecelia Parker. [Her father was born with the name Hugh Seymour Ker but on 27 June 1836 his name was legally changed to Hugh Seymour McDonnell by Royal Licence.] She married Rear-Admiral Sir Malcolm MacGregor, 4th Bt. on 26 October 1864.

Lady Helen Laura MacGregor of Edinchip, Balquidder, Perthshire, died on 17 March 1922, at the age of 84.