Short answers, pulled from the story.
Mary Boleyn (c. 1499 - 19 or the 30th of July 1543) was an English noblewoman, the sister of Queen Anne Boleyn, and one of the mistresses of King Henry VIII. She is also rumored to have been a mistress of King Francis I of France during the years 1515 to 1519, and there is speculation that Henry VIII fathered her two children, Catherine Carey and Henry Carey, though he never acknowledged either.
It is rumored but not confirmed that Henry VIII fathered Mary Boleyn's two children, Catherine Carey (born 1524) and Henry Carey (born the 4th of March 1526). Henry never acknowledged either child as his own, despite having previously acknowledged an illegitimate son by another mistress, Elizabeth Blount.
Mary Boleyn was banished from court in 1534 after her secret marriage to William Stafford, a soldier of modest means, was discovered when she became pregnant. Her sister Queen Anne Boleyn was furious at the match, which was considered beneath Mary's station, and the Boleyn family disowned her.
In a letter to Thomas Cromwell, Henry VIII's chief adviser, Mary wrote that she would rather beg her bread with William Stafford than be the greatest queen in Christendom. She acknowledged she might have chosen a man of higher birth but never one who loved her as well, and she believed Stafford would not forsake her to be a king.
Mary's daughter Catherine Carey became chief lady of the bedchamber to Queen Elizabeth I, and her son Henry Carey was ennobled by Elizabeth shortly after her coronation and made a Knight of the Garter. Elizabeth I offered Henry the Boleyn family earldom of Ormond as he was dying, but he declined it. Catherine Carey's daughter Lettice Knollys became the second wife of Robert Dudley, 1st Earl of Leicester.
Mary Boleyn has been played by several actresses in adaptations of her story: Natascha McElhone in the BBC film The Other Boleyn Girl (2003), Scarlett Johansson in the theatrical film The Other Boleyn Girl (2008), Perdita Weeks in the Showtime series The Tudors (2007-2010), and Charity Wakefield in the miniseries Wolf Hall (2015). Philippa Gregory's 2001 novel The Other Boleyn Girl was the source for both film adaptations.