Unfortunately, his only legit son, another William, was partying w/ his pals on a Channel cruise, the mead was flowing, & apparently no one was paying much attn to steering. This was known as the Tragedy of the White Ship b/c BAM natch it hit a passel of rocks b/c it got stormy & busted up & kilt everyone on board, incl a few of the bastard sibs that were of an age to be partying w/ bro Will. Everyone was gloomy b/c that meant Henry's legit daughter Matilda, Empress of Germany, was now his heir, & peeps didn't take kindly to being ruled by chicks in those times.
Henry got married again quicklike to Adelicia of Louvain, but alas he was old & his astonishingly active little swimmers had gotten sluggish so there were no more little Henrys forthcoming. Matilda's hubby demised & she had no kidlets, either, but Henry made all his peeps swear allegiance to her anyway & married her off to a boy practically half her age called Geoffrey, Count of Anjou, in the hopes of legit issue. Matilda & Geoffrey were unfussed w/ this whole thing but eventually they done their duty & produced 3 lads for England, Henry, Geoffrey Jr, & William. Good thing b/c Henry was getting mighty old for that time when the average life expectancy was like 35.
But when Henry demised aged 66 (of a surfeit of lampreys, tis said, which means he was a greedy pig & ate far too many eels in one sitting), his nevvy Stephen of Blois, son of his sister Adela, was just as sneaky as Henry had been & scampered over to claim treasury & crown for his good self HA HA. Henry's peeps said OK b/c no one liked Matilda. Matilda was furious & said I don't think so & commenced warring.
This is known as the period when Christ & all His saints slept b/c there was anarchy & chaos & famine & really cold winters where even the Thames froze over & some of the peeps used the war btwn the 2 claimants to plunder & pillage their neighbors just b/c they could. 1st Stephen captured Matilda, but she escaped across the frozen Thames in a snowstorm wearing white, which was right clever, dontcha think? Then Matilda captured Stephen, but in the meantime his peeps captured Matilda's bastard bro & head military peep Robert of Gloucester, so the prisoners were exchanged. No one was getting anywhere in this civil war & suffice to say it wasn't a nice time to visit England. Despite having the requisite set of cojones, Stephen wasn't a very good king & so peeps kept vacillating back & forth as to if he or Matilda were the lesser of 2 evils so lots of backstabbing. Finally Stephen's heir, Eustace, dropped dead, so an agreement was reached whereby Matilda would be passed over entirely & her eldest son Henry of Anjou would succeed Cousin Steve to the throne.....