Complex sentence: John Leverett was born, perhaps, in Boston, Lincolnshire where he is thought to have been educated at Boston Grammar School before emigrating to Boston, Massachusetts with his father in 1633, where was educated at the Boston Latin School.
Split into simpler sentences: John Leverett was born, perhaps, in Boston, England. He emigrated to Boston, Massachusetts with his father in 1633, and was educated at the Boston Latin School.