[3][4] In 1835, he married Jean Wedderburn, daughter of James Wedderburn and Isabella Clerk, and they had at least eight sons and five daughters, including: John (born 1843); James (1845–1892); Peter (born 1847); Andrew Cathcart (1851–1887); Colin George (1853–1888); Hugh (born 1855); Adam Gillies (1858–1891); Arthur Octavius (1862–1889); Isabella; Rebecca Marion (died 1914); Jean; Helen Agnes; and Mary.
[5][6][2][7][8][9] Blackburn started his career in the military as a cornet in the 2nd Regiment of Life Guards in 1830, before retiring as a lieutenant in 1837.
[10][8][9] A Liberal-Conservative, Blackburn was elected MP for Stirlingshire at a by-election in 1855, caused by the death of William Forbes.
In correspondence between the-then Chancellor of the Exchequer Benjamin Disraeli and Edward Smith-Stanley, 14th Earl of Derby, sent in August 1858, Smith-Stanley said: "Blackburn would be a respectable appointment, but there is no particular reason for him.
[11] While being recognised as "shrewd, energetic and practical" in his role, his defeat was credited to impolite actions regarding the commercial treaty, the county franchise, and game laws.