Between 6 July (date of marriage jointure) and 8 August 1653 (date of letter mentioning his changed condition because of marriage), Nathaniel Sylvester married Grizzell Brinley, daughter of Thomas Brinley, one of the Auditors General of the Revenues for Charles I, and later for Charles II.   

When Grizzel married, she brought with her to Shelter Island a family of enslaved people Jacquero and Hannah, and their daughter Hope, and another daughter eventually born on Shelter Island , Isabel : https://www.sylvestermanor.org/slavery-at-the-manor/hannah-jacquero-hope-isabell/  This family remained her personal property for the rest of her life.

Hannah’s daughter Isabell was given to 14-year-old Elizabeth Sylvester, and when she married in 1686, Isabell went with her to live in Southold. (Southampton)   This was perhaps the first time the family had been separated since arriving on Shelter Island. Grizzell died in 1687 and her Will bequeathed Hope to her daughter Elizabeth as well. Hannah and Jacquero were left to her three unmarried daughters still living at the Manor. , 

Grizzell was a younger sister of Anne Brinley, who in England had married Governor William Coddington of Rhode Island in January 1650. When the Coddingtons returned to Rhode Island in mid-1651, Grizzell came along as a ward of Coddington. Grizzell and Anne's brother, Francis, would join his sisters in the New World, fleeing Cromwell's England and establishing the American Brinleys in Newport, RI, and Boston, Mass.

Another Brinley sister, Mary, would marry Nathaniel's brother, Peter Sylvester. The Sylvesters were friends with Quaker founder George Fox, whom he entertained on at least one occasion on Shelter Island. They offered a place of refuge for several of the persecuted early Quakers in New England when it was dangerous to do so. Nathaniel Sylvester died in 1680.

Grizzell and Nathaniel had 11 surviving children. She was 17 years old when she married and 52 at her death.   The house on Shelter Island where she and Nathaniel raised their family was built in 1652, but a grandson rebuilt the house to be a much larger house.

See additional reading here courtesy of the Sylvester Manor :  https://www.sylvestermanor.org/sylvester-family/