The only real way to save the alliance was to have Henry marry Catherine. But marrying your brother's widow was extremely frowned upon by the church, so his father had to find a way to persuade the pope.
It was said that King Henry VIII and Catherine of Aragon had an unusually good relationship. Henry still married her after his father's death and the two loved each other a lot. Henry was quite a romantic and preferred to marry women based on love.
Sadly, this love didn't last forever. Catherine failed to give Henry an heir and his eyes began to stray towards Anne Boleyn.
Anne Boleyn was a smart woman and didn't want to just be Henry's side chick. She had her sights set for queen. She convinced Henry to divorce Catherine, and after a painstaking 2-year long divorce trial she finally became queen.
Anne was a great queen and influenced Henry with her reformist ideas. It was because of her that Henry cut off England from the Catholic church in Rome, which was a huge deal in terms of English history. Things quickly turned sour for Anne Boleyn, though, as she was caught insulting Henry's manliness and flirting with other men.
After getting a forced confession out of one of her pursuers, Anne Boleyn was beheaded in 1536. She left Henry with one daughter, Mary.