Fun Fact: On August 15, 1402, King Enrique III of Castile and León signed a peace treaty with his brother-in-law, King João I of Portugal. This treaty ended a conflict between Spain and Portugal that had begun in 1396. Remarkably, the wives of both kings—Catherine of Lancaster and Philippa of Lancaster—were sisters, symbolizing how family and diplomacy helped bring about peace during that era.by johnataylor on TwosFun Fact: On August 15, 1402, King Enrique III of Castile and León signed a peace treaty with his brother-in-law, King João I of Portugal. This treaty ended a conflict between Spain and Portugal that had begun in 1396. Remarkably, the wives of both kings—Catherine of Lancaster and Philippa of Lancaster—were sisters, symbolizing how family and diplomacy helped bring about peace during that era.