When John Milledge Brannen Jr. was born on 8 January 1809, in Georgia, United States, his father, John Milledge Brannen Sr., was 20 and his mother, Eleanor Ellen Baggs, was 23. He married Eliza Bonnell about 1824, in Columbia, Florida, United States. They were the parents of at least 5 sons and 9 daughters. He lived in Florida, United States in 1870 and Election Precinct 1 Columbia, Columbia, Florida, United States in 1880. He died on 19 February 1881, in Hamilton, Florida, United States, at the age of 72, and was buried in Prospect, New Haven, Connecticut, United States.