King William the Conqueror was the first ruler of the English Empire during Let's Play: Medieval 2 - Total War. He laid the foundations for his successors, ultimately turning his kingdom into a full empire.
Prior to ascending to the English throne, William was simply the Duke of Normandy, an independent region in northern France. He married Matilda of Flanders in 1053, who blessed the man with several children. Rufus was born in 1054, their daughter Cecilia in 1055, and their second son Robert in 1056. During this time, Edward the Confessor, King of England, was rescued by William from a shipwreck. In gratitude, the childless monarch named William as his successor. When he died in 1066, a man named Harold attempted to claim the English throne from William, only for the Duke of Normandy to crush him in the Battle of Hastings. He was crowned that same year, earning him the title King William the Conqueror.
While he earned his title well, and indeed sought to conquer more, King William understood the need for a proper family. Learning from the recent succession war, he wanted to ensure a secure line of heritage for his throne. England remained out of world politics for the next fourteen years as King William raised his family (including a third son, Henry, born in 1068) and incorperated Normandy into an overall English identity. Finally, the doors of England opened once more as diplomat Laurence Bidell secured trade rights with France in 1080. In that same year, he consented to marry his daughter Cecilia to Prince Edward Canmore of Scotland, hoping that he could secure a bloodline claim to Scottish lands.
King William knew he was growning old by this time, so he would never again step on the battlefield. Instead, he allowed his sons to conquer new lands in his stead. Prince Rufus claimed the renegade north by securing York in 1082, expanding England for the first time since his initial conquest. His son Robert married that year, and Prince Rufus married the year after. To William's delight, Rufus produced a grandson, Hubert, in 1084. Additionally, his third son Henry came of age, moving to Nottingham to assemble his own army. Later that year, Caernarvon was conquered by Prince Rufus, giving England rule over Wales. Rennes fell to Robert in 1086, leaving Henry as the only son not to conquer territory. As such, he arranged for Rufus's successful army to merge with Henry's, allowing his youngest son to conquer the rest of Britain.