Maid Marian according to Wikipedia
In narrative terms, Maid Marian was first attached to Robin Hood in the late sixteenth century as Robin was gentrified and given a virginal maid to pine after. Her biography and character have been highly variable over the centuries, being sometimes portrayed as a pagan or Saxon and other times as a high born Norman. (Marian's role was not entirely virginal in the early days. In 1592, Thomas Nashe described the Marian of the later May Games as being played by a male actor named Martin, and there are hints in the play of Robin Hood and the Friar that the female character in these plays had become a lewd parody.)
In an Elizabethan play, Anthony Munday made her a pseudonym of Matilda Fitzwalter, the historical daughter of Robert Fitzwalter, who had to flee England because of an attempt to assassinate King John. (The naming of Marian as 'Fitzwalter' betrays considerable ignorance on the part of the authors that introduced this name. Robert Fitzwalter was named so, because his father's name was Walter: it is not in any sense a surname. Marian would have been called 'Fitzrobert', after her father.) This was legendarily attributed to King John's attempts to seduce Matilda. The ballad of Robin Hood and Maid Marian which dates at least to the 17th Century presents a more active Marion who disguises herself as a page and (unrecognised) holds her own against Robin himself in a sword fight.
In the Victorian era she reverted to her previous role as the dainty maid. This highborn woman appears in many movies, under various characters: in The Adventures of Robin Hood, she is a courageous and loyal woman, whose initial antagonism to Robin springs not from aristocratic disdain but out of dislike of robbery; in The Story of Robin Hood and His Merrie Men, she, though a lady-in-waiting to Eleanor of Aquitaine during the Crusades, is a mischievous tomboy capable of escaping over the countryside disguised as a boy. With the rise of modern feminism in the 20th century, the character has often been depicted as an adventurer again, sometimes as a crack archer herself. In modern times, a common ending for Robin Hood stories became that he married Maid Marian and left the woods for a civilised, aristocratic life.
Marian's actual connection to the Plantagenet royals tends to vary. Generally she is depicted as a high-ranking lady of the court. In the famous Errol Flynn film, she is a ward of the court, an orphaned noblewoman under the protection of King Richard. In the Kevin Costner epic Robin Hood: Prince of Thieves, she is a maternal cousin to the sovereign while in the BBC TV Show adaption of 2006, she is the daughter of the former Sheriff and was betrothed to Robin prior to him leaving for the Holy Land. Possibly the oddest connection is found in the animated Disney Robin Hood; it is stated that Maid Marian is King Richard's niece, even though she is depicted as a fox and he as a lion, and Maid Marian is not treated as a royal although she does live in Nottingham Castle.