John of England and Isabella of Angoulême
In 1200, John married for the second time. He had the first declared invalid due to consanguinity, meaning he "discovered" that he and his wife were blood-related. His second wife was 20 years younger than him and became his wife entirely against her will - he kidnapped her from her fiancé, Hugh X of Lusignan. He also had his nephew killed and imprisoned his niece until she died. No wonder he is always depicted as the evil king Robin Hood was always battling. Another thing - dude liked to get around. He had at least 12 documented illegitimate children, in addition to the five he had with his kidnapped wife. In a 2006 poll, he was declared the 13th worst Briton of all time.
George I of Great Britain and Sophia Dorothea
First cousins George and Sophia married in 1682. It went fine for a while and they had a couple of kids before George decided he would rather be with his mistress, whom he also had two children with. Sophia was having an affair of her own with a Swedish Count. As was the case with Kings and Queens back then, it was OK for him to have an affair, but not her. The Count was "mysteriously" murdered in 1694 and the Royal marriage was dissolved on the grounds that Sophia Dorothea had abandoned her husband. She was imprisoned in a castle for more than 30 years and not allowed to see her children or parents, nor was she allowed to remarry.
Christian VII of Denmark and Princess Caroline Matilda of Great Britain
Caroline and her cousin Christian were married in 1766, when Caroline was only 15. In 1767, he publicly announced that he did not and could never love his wife; it simply wasn't fashionable to love the person you were married to. It eventually became clear that Christian had some mental problems. His symptoms included paranoia, self-mutilation and extreme hallucinations. The neglected Queen began having an affair with her husband's doctor. They were discovered and arrested in 1772; the doctor was executed and Caroline was deported to Germany. She and the King divorced and she never saw her children again.
George IV of the United Kingdom and Caroline of Brunswick
This marriage was doomed pretty much from the start. The first-cousin bride and groom found each other quite unattractive; he even went so far as to call Caroline unhygenic. He had already secretly married but this was declared invalid due to the Royal Marriages Act 1772 (members of the British Royal family under the age of 25 are not allowed to marry without the consent of the current monarch). George revealed that the couple had sex a grand total of three times, and all of these occurred during the first two days of marriage. One of these instances did result in a daughter, however. The couple stopped living together almost immediately, made separate public appearances and had no qualms about assuming numerous other lovers. Caroline was not allowed to see her daughter every day and was sent to live in a private residence. In 1814, while she was traveling abroad, her daughter died after giving birth. Caroline was only told of her daughter's death when her son-in-law wrote her. She came back to Britain in 1820 when her husband ascended to the throne but was turned away from the coronation. The same night, she fell mysteriously ill and couldn't stop vomiting; she was convinced she had been poisoned and may have been right: she died three weeks later but was never given an autopsy.
Henry VIII and Katherine of Aragon, Anne Boleyn, Anne of Cleves and Catherine Howard
There was also Jane Seymour and Catherine Parr, of course, but Jane Seymour died after childbirth and Catherine Parr outlived Henry. The other wives weren't so lucky. First, Henry married Katherine of Aragon, his brother's widow. Then he fell in love with Anne Boleyn and ditched Katherine just as soon as he could; she was lucky that he only had the marriage annulled and didn't dig up a reason to execute her. He did send her off to a dank, crappy castle to die and refused to let her daughter visit. Even when she did die, the Princess Mary wasn't allowed to go to the funeral. Rumor has it that when he received the news of Katherine's death, Henry outfitted himself in yellow clothes - yellow was the color of celebration at the time. After his second wife Anne Boleyn miscarried several babies and could not produce a male heir, he declared that he had only married her because he had been under the influence of witchcraft. He had her beheaded and refused to even provide a proper coffin; Anne was buried in an arrow chest. Next to experience Henry's wrath was fourth wife Anne of Cleves. He married her begrudgingly and had only seen a painting of her. When he met her in person, he found her exceedingly unattractive but married her anyway, only to have it annulled after about six months. Thereafter, she was referred to as the King's Sister. Next up was Catherine Howard, a young girl who was rather grossed out by her nearly 50-year-old husband, who was about 300 pounds and had an ulcer on his leg that had to be lanced and drained every day and smelled horribly. She had an affair with a man in the King's Court, the King found out and had Catherine beheaded.