Complex sentence: The Duke had offered to raise a new regiment for the King, who objected, however, to the Duke's desire to confer the colonelcy upon his brother Lord William Gordon, who had disgraced himself by eloping with and then abandoning Lady Sarah Bunbury.
Split into simpler sentences: The Duke had offered to raise a new regiment for the King, with the intent of bestowing the colonelcy upon his brother, Lord William Gordon. King George objected, however, to Lord William, who had disgraced himself by eloping with and then abandoning Lady Sarah Bunbury.