Henry VIII was the only King of England to have all three of his children inherit the throne. Typically, all a King’s children would be in the succession until the King died. Not so if the King is Henry VIII! 

Desperate for a son, Henry actually disinherited both of his daughters. He disinherited Mary when Elizabeth born (the First Succession Act was passed in 1534) because he claimed the marriage to Katherine of Aragon was not valid. He disinherited Elizabeth when killed her mother (the Second Succession Act was passed in 1536) because he claimed the marriage to Anne Boleyn was not valid. For several years after he was born, Edward was only heir. Finally, in 1543, Henry enacted the Third Succession Act, which returned Mary and Elizabeth to the succession. 

All these changes affected the children as they grew and then as all three took the throne. Their relationships with Henry, with various stepmothers, and with each other shaped the rest of their lives.

History shows us what's possible.