Ever since I saw the Masterpiece Theater mini-series The Six Wives of Henry VIII in 1970, I've been fascinated by the Kings and Queens of England. Then I took a course in Arthurian Legend in college and found out about Henry II and Eleanor of Acquitaine. Being a theater major, I took a Shakespeare course and got introduced to Henry V and Richard III.
Well, I recently bought two books by Dan Jones: the Plantagenets, which traces the royal history from William the Conqueror to Richard II, and The War of the Roses, which picks up the story with Henry IV through Henry VII. Man oh man -- now there was a family who didn't get along! These people were always fighting wars over who would rule. And if they weren't fighting each other, they were fighting France. If you were on the wrong side, you could literally lose your head.
It seems like every good, strong, long-lasting king was followed by either an ineffectual weakling (Edward II, Henry VI) or an out and out tyrant (Richard II). (Well, except for Henry III's son Edward I -- he was a strong king.) But when the weak kings rules, some faction of relations would get pissed off because of jealousy or spite or frustration, raise an army, and rebel. In some cases, a strong king died only to leave a kid as king. Sometimes the kid grew up and became a pretty strong king (Henry III, Edward III); other times the poor kid didn't even get a chance to reign before disappearing under mysterious circumstances (Edward V).
Anyway, after the Plantagenet dynasty shit the bed (because Richard II was a horrible guy), the House of York and House of Lancaster took over with the bloody bickering. First the Lancaster faction was on top (Henrys IV, V, and VI) then the York faction yanked the throne for themselves (Edward IV, Edward V (the kid who disappeared), Richard III) and finally the Lancaster faction found a guy who could trace his lineage back to Edward III (it was pretty weak, actually) and he whacked Richard III at Bosworth and claimed the throne as Henry VII, beginning the Tudor dynasty.
And that's your history lesson for the day! Are you confused?