John Winslow belonged to one of the most prominent families of New England; his great-grandfather Edward and grandfather Josiah Winslow had both been governors of the Plymouth Colony. He was born in Marshfield, Massachusetts in 1703 as son of Sarah and Isaac Winslow. In 1725, he married Mary Little, a descendant of Pilgrim Richard Warren. They had three children: Josiah, Pelham and Isaac Winslow. One of his slaves was Briton Hammon who published the Narrative of the Uncommon Suffering and Surprizing Deliverance of Briton Hammon, a Negro Man in 1760.