He was the son of Sir Francis Godolphin Osborne, fifth duke of Leeds by his second marriage, the first having ended in divorce after Amelia Darcy (mother of Augusta Leigh) eloped with Byron's father.

CORRESPONDENCE OF Lord Sidney Godolphin Osborne:

Lord Byron to Lord Sidney Godolphin Osborne, 9 February 1824 in A Narrative of Lord Byron’s Last Journey to Greece. Extracted from the Journal of Count Peter Gamba, who attended that Expedition. (London: John Murray, 1825)