Wars of the Roses
Lancastrian claim

The House of Lancaster descended from John of Gaunt, the third surviving son of Edward III. The name derives from Gaunt's primary title as Duke of Lancaster, which he held by right of his spouse, Blanche of Lancaster. The Lancastrian claim on the throne had received preference from Edward III which explicitly emphasised the male line of descent. Henry IV based his right to depose Richard II and subsequent assumption of the throne upon this claim, since it could be argued that the heir presumptive was in fact Edmund Mortimer, the great-grandson of Edward III's second surviving son, Lionel, Duke of Clarence. However, Mortimer was descended through the female line, inheriting the claim from his grandmother, Philippa. An important branch of the House of Lancaster was the House of Beaufort, whose members were descended from Gaunt by his mistress, Katherine Swynford. Originally illegitimate, they were legitimised by an Act of Parliament when Gaunt and Katherine later married. However, Henry IV excluded them from the line of succession to the throne.
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