Queen Elizabeth I of England and Mary, Queen of Scots were two of the greatest, most legendary rivals in recorded history although they never even met.

Mary and Elizabeth were first cousins once removed through King Henry VII of England. Two of Henry VII’s eight children were Henry VIII Tudor and Margaret Tudor. Margaret went to Scotland and married James IV; their son, James V, had Mary with his second wife, Mary of Guise. Six days after Mary was born, King James V died, rendering her Queen of Scotland.
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Now, onto Elizabeth’s side of the family. Henry VIII succeeded his father, Henry VII, on the throne. Famously, Henry VIII broke with the Catholic Church in Rome so he could marry Anne Boleyn after his first wife, Catherine of Aragon, did not produce a male heir (they had a daughter, Mary, together). Henry VIII married Anne in a secret ceremony (then he went on to get married four more times). Anne Boleyn didn’t produce a male heir, either: Elizabeth was the only child of Henry VIII and Anne Boleyn. Henry VIII later had Anne beheaded. Henry VIII finally had his much-desired male heir, Edward, with his third wife, Jane Seymour.

In 1558, Elizabeth finally became Queen of England and Ireland — though it was a dramatic path to the throne. Elizabeth’s half-brother, Edward I, was crowned King in 1547 when he was 9 years old. Edward, always a sickly boy, died at age 15.

According to the preexisting succession plan, the throne was to go to Edward’s Protestant cousin Lady Jane Gray. Nine days after Jane took the throne, Elizabeth’s half-sister, Mary Tudor, had her executed and took the throne herself in what historian Anna Whitelock describes as “an extraordinary coup d’etat.” Mary enacted a violent campaign to turn England back into a Catholic country, earning herself the nickname Bloody Mary. Finally, after Mary’s death in 1558 at age 42, the throne went to Elizabeth, who was Protestant. But even that was contested. Catholics believed Elizabeth the product of an unlawful marriage, and thus not a legitimate heir to the throne.

Which brings us to Mary, the only surviving child of her father, King James V of Scotland. In Catholic eyes, after Mary Tudor’s death, there were no more rightful heirs that descended from King Henry VIII. To find an heir, one had to go back to Henry VII’s descendants — which made the Catholic Mary Stuart, not Elizabeth, the rightful successor to Mary Tudor’s throne. Mary refused to ratify the 1560 Treaty of Edinburgh, which would declare Elizabeth the uncontested monarch of England.

Bloodily. What else did you expect? In 1567, Mary Stuart was deposed from the throne of Scotland. She fled to England in 1568, expecting her cousin Elizabeth to provide protection. Instead, Elizabeth put her on house arrest. Nineteen years of captivity later, Mary was allegedly the focal point of various conspiracies to overthrow Elizabeth. On February 8, 1587, Mary was beheaded for treason.

In 1603, Mary’s son, James VI, succeeded Elizabeth on the throne. He became king of England, Scotland, and Ireland. The kingdoms were finally united under one crown.