If I had to pick one medieval event I particularly dislike, it's the War of the Roses, a fancy name for an English civil war that took place in the 1400s. The cause of this dispute was succession: Edward III had a ridiculous amount of children, but the ones of interest are Edward, Lionel, John, and Edmund. Edward was the Prince of Wales, heir to the throne, but he died before Edward III. His son became Richard II, but he was a particularly shitty king, and several nobles in the kingdom rebelled and deposed of him. Now according to the line of succession, we have then to look at Edward III's next son, Lionel. He died about thirty years prior, but his great-grandson Edmund was alive... unfortunately as a nine-year-old kid. And no kingdom wants a child ruler with its regent and council fighting amongst themselves. But the leader of the rebellion, Henry, said Lionel only had a daughter, Philippa. So Edmund gets his claim through his grandmother. And women don't count unless there's no other resort. However Edward III had other sons, so let's move onto son number three, John. John's also dead, but his son is alive... who happens to be the leader of the rebellion, Henry. So Henry took the throne and everyone ignored Edmund. In case you're confused, here's a little chart to explain shit:

To recap, Richard II sucks, Henry IV kills him, says Edmund doesn't count because Lionel only had a daughter, Henry IV takes kingship because if you ignore Lionel he's next in line. His family is known as the House of Lancaster because he's the duke of Lancaster. He has a son who becomes Henry V, and Henry V has a son who becomes Henry VI. Here's another chart to keep you on point:

The problem is Henry VI was also a child king, about eight months old to be exact. England entered the same situation they were trying to avoid two generations ago. After experiencing a terrible time during his minority, the English thought they'd finally get a respite when Henry VI came of age. Unfortunately like Richard II he was a shitty king too. So once again nobles started rebelling. This is when it gets complicated. Edward III's fourth son, Edmund, had a grandson named Richard. Remember poor little Edmund, great-grandson of Lionel, who got passed over? He had a sister named Anne, who married Richard:

Richard said, "Wait a second. I don't care what we decided generations ago. Edmund was supposed to be king! And because he's dead now, I should be king because I'm married to his sister!" He died during the uprising, but his son eventually won the war and became Edward IV. Because they were the dukes of York, their family became known as the House of York. It's called the War of the Roses because (supposedly) the House of Lancaster had a red rose on their family crest and the House of York had a white one. When Edward IV died once again only children were left behind, Edward V and Richard. They were placed under the care of their uncle, also confusingly named Richard. We can't prove it, but it's most likely both of them were killed under Richard's orders so he could become King Richard III:

In case you're completely lost right now, I can assure you it's about to get a lot worse. Once everyone realized what Richard III did, he received condemnation from huge portions of the kingdom, although he retained a good portion of loyalty from the north. At some point a guy named Henry Tudor said he was the last heir to the House of Lancaster, meaning he'll retake the kingdom from those Yorkist bastards once and for all. Well, his claim was flimsy at best. Henry V married a woman named Elizabeth, and when he died she remarried a dude named Owen Tudor. Owen is Henry's grandfather. As I said, flimsy at best. "My dad was Henry VI's half-brother" doesn't really cut it, especially since Owen Tudor was a nobody from Wales.

But all that mattered was Henry beat and killed Richard III in battle, so by right of conquest he became King Henry VII of England. And being the last "heir" of Lancaster, he married Edward V's sister Elizabeth. The Tudor family usually displayed a white and red rose as their symbol to show how the House of Lancaster and York united with Henry and Elizabeth.

Do you understand why I hate this conflict? Because it's so fucking confusing remembering who's related to whom and how. And this is just the bare basics. Do you remember way back in the beginning I said Edward III had a lot of kids? All the descendants of those siblings were involved, and it turns into a giant clusterfuck. This genealogy from wikipedia barely scrapes the surface of the players. It doesn't show the Beauforts, the Nevilles, Warwick the Kingmaker, or any of that shit. Just the people directly involved with the royal family. Every single time I read a book about this, I need to keep copious amounts of notes to remember who is who and what their allegiance is. It doesn't fucking help that people were unimaginative and only had about ten names to choose from for their kids. After the fortieth Edward you kinda want to shoot yourself in the foot.

I would like to deeply apologize for my poor MS Paint skills.