What if Black Prince was widowed not long after birth of Richard II and marries Constance of Castile, OTL duchess of Lancaster as his second wife (John of Gaunt likely marries her sister Isabel instead). Say that Black Prince has at leas one child with her. What would be effects? Most obvious one-John of Gaunt's Iberian adventure is butterflied away-his brother's wife has better claim to Castile ITTL than his own wife. As Gaunt's attempts to get Castilian throne failed anyway, it would be good thing for him-he would not waste resources for such fruitless campaign. Balck Prince's half Castilian child OTOH would be too young to be serious claimant. That means also that Anglo-Portuguese alliance is weaker than IOTL without Gaunt's involvement.