What was the relation of Mary, Queen of Scots, to Queen Elizabeth I?

Mary, Queen of Scots, and Queen Elizabeth I's relationship is a fascinating, and ultimately tragic, chapter in British history. To understand it, we need to look at the Tudor family tree. Both women were descendants of Henry VII. Elizabeth was Henry VII's granddaughter through his son Henry VIII, while Mary was his great-granddaughter through his daughter Margaret. This makes them cousins, not sisters or mother and daughter. The Stuart claim to the English throne came through Margaret Tudor's marriage to James IV of Scotland. Because Elizabeth I had no direct heir, Mary, being her closest relative with a strong claim, was next in line, which is why she posed such a threat to Elizabeth's reign. Many Catholics believed Mary was the rightful Queen of England, adding to the political tension. Ultimately, Elizabeth had Mary executed, a decision that haunted her. So, while they were both powerful queens, their family connection was that of cousins, linked through the complex web of royal lineage.