Complex sentence: Pierre was among the children of Jean and Marie-Jeanne Bonga, a slave couple who with their family had been brought to Mackinac Island by Captain Daniel Robertson, commander of the fort there from 1782 to his death in 1787.
Split into simpler sentences: Pierre was among the children of Jean and Marie-Jeanne Bonga, a slave couple. With their family, they had been brought to Mackinac Island by their master Captain Daniel Robertson, commander of the fort there from 1782 to his death in 1787.