Wars of the Roses
Succession crisis

The question of succession following the death of Edward III in 1377 is said by Mortimer to be the root cause of the Wars of the Roses. Although Edward's succession seemed secure, there was a "sudden narrowing in the direct line of descent" near the end of his reign; Edward's two eldest sons, the heir apparent Edward, Duke of Cornwall ("the Black Prince") and Lionel, Duke of Clarence, had predeceased their father in 1376 and 1368 respectively. Edward III was survived by three sons with claims to the throne: John of Gaunt, Duke of Lancaster; Edmund of Langley, 1st Duke of York; and Thomas of Woodstock, 1st Duke of Gloucester.

The Black Prince had one surviving son, Richard, who had a claim to the throne based upon the principle that the son of the heir apparent (Edward, in this case) had priority in the line of succession over his uncles. Thus, Richard had a superior claim to the throne than his much older uncles: John, Edmund and Thomas. However, Richard was a minor; had no siblings; and his three living uncles (at the time of Edward III's death) were politically powerful and ambitious, so there was considerable uncertainty within the realm over who should inherit the throne. Ultimately, Edward was succeeded by his grandson who was crowned Richard II at just 10 years old.

Under the laws of primogeniture, if Richard died without a legitimate heir, his successors would be the descendants of Lionel of Antwerp the Duke of Clarence, Edward III's second eldest son. Clarence's only child, his daughter Philippa, married into the Mortimer family and had a son, Roger Mortimer, who technically would have the best legal claim of succession. However, a legal decree issued by Edward III in 1376 introduced complexity into the question of succession, since the letters patent he issued limited the right of succession to his male line, which placed his third son, John of Gaunt, ahead of Clarence's descendants, since the latter were descended through the female line.
punctuation:no_comma