[NI0841]
57 yrs old when married. source: New Letters of Robert Southey Vol. I 1792-1810 by Kenneth Curry, Prof. of English, University of Tennessee, Columbia University Press Ltd. (1965) p. 491
See also the footnote #3 which states;
"Alfred, Georgiana and Southey Hill were the three youngest of the children of the Reverend Herbert Hill. The three eldest boys-Edward, Herbert, and Erroll-are frequently called Duke, Marquess, and Earl."