Grenfell married Lady Georgiana Frances, daughter of
William Molyneux, 2nd Earl of Sefton, in 1819. They had two sons,
Charles Grenfell and
Henry Grenfell, and two daughters, Maria Georgiana, who married
Frederick Paget, and Louisa Henrietta, who married Theodore Walrond. The family lived at
Taplow Court,
Taplow,
Buckinghamshire. Lady Georgiana died in June 1826. Grenfell survived her by over 40 years and died at his home,
Taplow Court, in March 1867, aged 76. ==References==