John of Gaunt John of Gaunt John of Gaunt, Duke of Lancaster (6 March 13403 February 1399) was an English prince, military leader, and statesman. He was the third of the five sons of King Edward III of England who survived to adulthood. Due to his royal origin, advantageous marriages, and some generous land grants, Gaunt was one of the richest men of his era, and an influential figure during the reigns of both his father, Edward, and his nephew, Richard II. As Duke of Lancaster, he is the founder of the royal House of Lancaster, whose members would ascend to the throne
Succession to Elizabeth I of England John of Gaunt, would claim the throne and so overturn the principle of primogeniture, was revived in the context of the Elizabethan succession, after seven generations. John of Gaunt's eldest daughter having married into the Portuguese House of Aviz, one of his descendants was the Infanta of Spain, Isabella Clara Eugenia. The legitimacy of Isabella's claim was seriously put forward, on the Catholic side of the argument. A reason given for Essex's Rebellion was that the Infanta's claim had gained traction with Elizabeth and her counsellors. The Succession to the Crown Act 1543 was the third such act of the