In March 1815, Melvill married Hester Jane Frances (died 10 April 1864), youngest daughter of William Marmaduke Sellon of
Harlesden in
Middlesex. They had nine children and at least 28 grandchildren: • Henrietta (1816–1900), married in 1844 Richard Beachcroft. Mother to Florence Henrietta Beachcroft, Sir
Melvill Beachcroft, Katherine Hester Beachcroft, Henry Audry Beachcroft, Emily Charlotte Beachcroft, the Rev. Charles Seward Beachcroft, Philip Edward Beachcroft and Annie Rachel Beachcroft. • Philip Melvill (1817–1854), administrator for the East India Company. Eventually became the Chief Commissioner for affairs in the Punjab in 1853. Married in 1845 Emily Jane Hogg. Father to Emily Hester Melvill, Alice Philippa Melvill and Philip Lawrence Melvill. • Fanny (1819–1894), married in 1854 the Rev. Henry Holme Westmore. • James Cosmo Melvill (1821–1880), administrator in British India. Later became Assistant Under-Secretary of State for India following the termination of the East India Trading Company. Married in 1844 Eliza Jane Hardcastle. Father to
James Cosmo Melvill, Marion Eliza Melvill, Evelyn Hester Melvill, Alfred Hardcastle Melvill, the Rev. Arthur Hardcastle Melvill, Emma Wilhelmina Jean Melvill, Selina Emily Melvill and Edith Mary Melvill. • Hester (1823–1911). Twin sister to Jean. Married in 1848 Col. Thomas Fenwick of the Royal Engineers. • Jean (1823–1911). Twin sister of Hester. • Marion (1826–1914), married in 1848 James Alexander Wedderburn Esq. of the Madras Civil Service. Mother to James Alexander Wedderburn and Marion Hester Wedderburn, who both died in infancy. Also mother to Alexander Dundas Ogilvy Wedderburn KC and Marion Hester Wedderburn. • Sir
William Henry Melvill (1827–1911), a barrister, called to the Bar of Lincoln's Inn and practised as a Junior until appointed Solicitor to the Board of Inland Revenue. Knighted for services in 1887. He married in 1862 the Honourable Elizabeth Theresa Lister, youngest daughter of
Thomas Lister, 2nd Baron Ribblesdale. Father to Russell Melvill, Harry Edward Melvill (Barrister of the Inner Temple and Private Secretary to Sir Edgar Vincent), Commander Francis William Melvill and Major James Lister Melvill. • Rachel (1831–1913). Married in 1862 the Rev. William Henry Brendon. Mother to Rachel Mary Brendon, who married in 1897 Henry Digby Cleaver Esq, himself descendant of
Isabel Plantagenet, Countess of Essex. Grandmother to Ronald Melvill Digby Cleaver. ==References and sources==