Complex sentence: Though both Livingston and Fulton had died by the time Vanderbilt went to work for Gibbons, the monopoly continued in the hands of Livingston's heirs, who had granted a license to Aaron Ogden to run a ferry between New York and New Jersey.
Split into simpler sentences: Though both Livingston and Fulton had died by the time Vanderbilt started working for Gibbons, the monopoly was held by Livingston's heirs. They had granted a license to Aaron Ogden to run a ferry between New York and New Jersey.