Mary was the daughter of King Henry VII of England and his former wife, Catherine of Aragon. She was the only surviving child between the two, and she grew up Catholic.
Eventually, Henry became unsatisfied with Catherine due to the fact she was never able to bear him a son. Henry eventually ended up divorcing Catherine, and despite him taking great pride in his daughter, Mary was exiled alongside Catherine.
Despite being the firstborn of Henry, due to her parent’s divorce she was no longer considered a legitimate child, and therefore lost her place in line with the throne.
However, Mary managed to reconcile with her father, gaining her spot as heir to the throne when his son, Edward I, died. However, Edward appointed his cousin, Lady Jane Grey to the throne. Shortly after Edward’s death, Mary started gaining supporters to eventually overthrow Jane.
The council that assisted Edward’s reign (due to the fact that he was very young when he first took the throne) eventually turned on Jane and backed Mary. And with enough support, Jane was imprisoned and executed after 9 days of being queen. Mary was officially Queen of England in 1553.
Mary being Catholic had a LOT to do within her reign. When she became queen, she set the bar for persecution higher than it was before, and due to this she was granted her nickname “Bloody Mary”. She set aflame to over 300 Protestants (yikes).
Her reign was short was however, as her life was taken in 1558 due to the influenza epidemic. She was buried in Westminster Abbey, and her sister Elizabeth I took over after her.