Margery Browne was born in Cork, Ireland, in 1714. She arrived in York, Maine, as a nine-year-old orphan, on a ship that also carried thirty-three-year-old Owen O'Sullivan. Owen was a well-educated man who came from a ruling family in Ireland. He soon Anglicized his name to John Sullivan, and after working a short time on a farm, he became a schoolteacher.

Master John Sullivan taught for many years in Dover and Somersworth, New Hampshire, as well as in Berwick, Maine. In 1735, despite their significant age difference, Master John Sullivan and Margery Browne were married in Berwick, Maine.

In 1743, it appears that John and Margery had a falling out. After John disappeared from the family farm for several days, Margery issued the following apology in the Boston Evening Post.

My dear and loving Husband,
Your abrupt Departure from me, and forsaking of me your Wife and tender Babes, which I humble acknowledge and confess I was greatly if not wholly on the Occasion of, by my too rash and unadvised Speech and Behaviour towards you; for which I now in this publick Manner humbly ask your Forgiveness, and here-by promise upon your Return, to amend and reform, and by my future loving and obedient Carriage towards you, endeavour to make an Atonement for my past evil Deeds, and manifest to you and the whole World that I am become a new Woman, and will prove to you a loving dutiful and tender wife.
If you do not regard what I have above written, I pray you to hearken to what your Pupil, Joshua Gilpatrick hath below sent you as also to the Lamentations and Cries of your poor Children, especially the eldest, who (tho' but seven Years old) all rational People really conclude, that unless you speedily return will end in his Death, and the moans of your other Children are enough to affect any humane heart....And why, my dear Husband, should a few angry and unkind Words, from an angry and fretful Wife (for which I am now paying full dear, having neither eat, drank nor slept in quiet, and am already reduced almost to a skeleton, that unless you favour me with your Company, will bereave me of my Life) make you thus to forsake me and your Children? How can you thus for so slender a Cause as a few rash words from a simple and weak Woman, chuse you to part from your tender Babes, who are your own Flesh and Blood? Pray meditate on what I now send, and reprieve you poor Wife and eldest Son (who take your Departure so heavily) from a lingering tho' certain Death, by your coming home to them again as speedily as you can, where you shall be kindly received, and in the most submissive Manner by your Wife, who is ready at your Desire, to lay her self at your Feet for her past Miscarriage and am with my and your Children's kind love to you, your loving Wife,
Margery Sullivan
Summersworth, New-Hampshire
July 11, 1743

As Margery was considered to be a strong-willed, quick-tempered and witty woman, it is difficult to judge the sincerity of the apology. Regardless, Master John returned and the Sullivans remained together until their deaths.

Margery and John were the parents of five sons and one daughter who were raised on the family farm in Berwick. Margery tended to the farm while Master John tended to the school. All but one of their children played important roles in the time before, during, and after the American Revolution.

Their first son, Benjamin, served in the Colonial Navy and was lost at sea before 1775.

Daniel, the second born, was a Captain of Minutemen. He was captured by the British and sentenced to a New York harbor prison ship after he refused to take an oath that he would not reenter the Continental Army. Through the intercession of his brother, General John Sullivan, Daniel was released after fourteen months of confinement, but died a day or two after leaving New York.

General John Sullivan was Margery and John's third child. John was a practicing lawyer in Durham, New Hampshire, prior to the American Revolution. Along with several townsmen, he was instrumental in the first act of aggression against the British crown at the capture of Fort William and Mary in December of 1775. As a Brigadier General and later, Major General of the Continental Army, John held commands at the siege of Boston, the battles of Princeton, Brandywine, and Germantown. Following the Revolution, John returned to New Hampshire as a hero. He later served as Attorney General, Governor, and United States District Judge for the state of New Hampshire.

Fourth son James served as Governor of Massachusetts from 1807 to 1808. An attorney like his brother, James served as a judge during the Revolutionary War and later served in Congress and was Attorney General for the United States.

Daughter Mary taught school in Durham at a time when women were rare in the profession. She married Theophilus Hardy. Her grandchildren include Samuel Wells, Governor of Maine; John Sullivan Wells, Speaker of the House and President of the New Hampshire Senate; John Bartlett Wells, Lieutenant Governor of Illinois; and Frederick Bert Wells, United States Consul to Bermuda.

The youngest child, Eben, served as a Captain in the Revolution. Captured and held hostage to guarantee a prisoner exchange, Eben was later released and went on to serve as an aide to his brother, John. He was present at the Battle of Bunker Hill.

Master John Sullivan died in Berwick at the age of 105. Margery died five years later in 1801 at the age of 82. They were both originally buried on the family farm, but in 1877 were transferred to the property of their son, John Sullivan, in Durham, New Hampshire.