Personal life
On 29 December 1803, Macdonald married Louisa Maria La Coast (1781–1835). She is said to have been the illegitimate daughter of Prince William Henry, Duke of Gloucester and Edinburgh (a son of Frederick, Prince of Wales and a younger brother of King George III) and his mistress, Lady Almeria Carpenter (a daughter of the 1st Earl of Tyrconnell), although she was baptised at Leatherhead in 1781 as the daughter of Farley Edser (a steward to the Duke of Gloucester who was a tenant of a dairy farm near Hampton Court). Together, they were the parents of thirteen children, including:
Alexander William Robert Bosville (1800–1847), de jure 12th Baronet, who married Matilda Eliza Moffat Bayard, a daughter of Col. John Bayard.
William Macdonald (1801–c. 1805), who died young.
Louisa Bosville Macdonald (1802–1854), who married John Hope, 5th Earl of Hopetoun.
Hon. Elizabeth Diana Bosville Macdonald (1804–1839), who married Duncan Davidson, 4th of Tulloch, a son of Henry Davidson of Tulloch, in 1825.
Hon. Julia Bosville Macdonald (1805–1884), who married the Rev. Charles Walter Hudson, a son of Harrington Hudson (MP for Helston) and Lady Anne Townshend (a daughter of the 1st Marquess Townshend), in 1838.
Hon. Susan Hussey Bosville Macdonald (1807–1879), who married Capt. Richard Beaumont, son of Col. Thomas Richard Beaumont (MP for Northumberland), in 1832.
Godfrey William Wentworth Bosville-Macdonald, 4th Baron Macdonald (1809–1863), who married Maria Anne Wyndham, eldest daughter and co-heiress of George Thomas Wyndham, of Cromer Hall, Norfolk, in 1845. Her sister, Cecilia, married Lord Alfred Paget (a son of the 1st Marquess of Anglesey).
Hon. James William Bosville Macdonald (1810–1882), a Lieutenant-General who was Aide-de-camp, Equerry and Private Secretary to Prince George, Duke of Cambridge; he married Hon. Elizabeth Nina Blake, daughter of Joseph Blake, 3rd Baron Wallscourt, in 1859.
Hon. Diana Bosville Macdonald (1812–1880), who married John George Smyth, MP for City of York who was a son of John Henry Smyth (MP for Cambridge University) and Lady Elizabeth FitzRoy (a daughter of the 4th Duke of Grafton), in 1837.
Hon. Jane Bosville Macdonald (1815–1888), who died unmarried.
Hon. Marianne Bosville Macdonald (1816–1876), who married Capt. Henry Martin Turnor, a son of Edmund Turnor, in 1840.
Hon. William Bosville Macdonald (1817–1847), who married Sophia Keppel.
Hon. Octavia Sophia Bosville Macdonald (c. 1819–1897), who married William James Hope Johnstone, the eldest son of John Hope-Johnstone, de jure 7th Earl of Annandale and Hartfell, in 1841.
Three of his children with Louisa were born before their marriage, so they were considered illegitimate, while the ten children born after their marriage were considered legitimate. The eldest three were eventually legitimized by Scottish law, but not by Irish law, therefore, the Scottish baronetcy passed to his eldest son, Alexander, while the Irish barony passed to his third son, Godfrey.
Lord Macdonald died on 13 October 1832 at Bridlington, in England. His widow, the dowager Lady Macdonald, died on 10 February 1835, at Bossall, Yorkshire.