Why is John Gaunt an important part of Henry VII's linage?

John Gaunt, Duke of Lancaster, is a crucial figure in Henry VII's lineage because he is the father of Henry IV and the founder of the House of Lancaster. Through his marriage to Katherine Swynford, Gaunt established a line of descent that ultimately contributed to the Tudor claim to the English throne. Henry VII, as a descendant of Gaunt's legitimized children, used this connection to strengthen his own claim after the Wars of the Roses, emphasizing the importance of Gaunt in the dynastic history of England.