In OTL Mary I of England and Philip II of Spain married in July of 1554. Though Mary adored her husband, he was actually repelled by her. Then in November of 1554 Mary convinced herself she was pregnant, though after it turned out this was simply a phantom pregnancy Philip III was disgraced and left for Flanders to fight the French, leaving Mary in a distressed way. This was furthered after, Mary was convinced by Philip to support him in the Italian Wars, this ultimately led to the recapture of Calais, the last English territory in France. This furthered Mary's death and she stated that 'when she died the words "Philip" and "Calais" would be found inscribed on her heart.'
But, what if in 1554, 5 months after the marriage between Mary I of England and Philip II of Spain, Mary was actually pregnant? And in March of 1555 Mary bares a child, a healthy baby boy. Due to this Philip II doesn't go to Flanders straight away to fight and instead stays with Mary. Again in 1556 Mary becomes pregnant in April through Philip II, and another healthy baby is born, though a girl this time.
This Alternate History is explored in these articles I will make.