Haytham was born in London. His father was Edward Kenway, a former pirate who trained him with a secret purpose. One day before his tenth birthday, young Haytham's home was burned, his half-sister Jenny was taken, and his father was killed. Reginald Birch, a family friend, offered to help and revealed he was a Templar, though the boy hardly understood what this implied at the time. Haytham was introduced to Edward "The Bulldog" Braddock, a soldier in the Royal Army and fellow Templar, and the two took an instant dislike to each other.
Years passed in a fruitless search for his half-sister, and Haytham and Birch settled in Troyes, France. Haytham became a ruthless and efficient killer for the Templars. While searching for his father's killer, he met Braddock in Germany and served in his Coldstreams unit in the War of Austrian Succession.
In 1754, Haytham killed in Assassin named Miko in London to acquire an amulet needed to find a First Civilization storehouse. Birch sent him to the colonies to establish an official Templar presence while he searched for the Precursor site. He secured the assistance of Kanien'kehá:ka natives by freeing several captives, including a woman named Ziio, with whom he had an ill-fated but passionate affair.
In 1755, Haytham got word from his European contacts that Jenny was found in the Ottoman Empire. He left the colonies to rescue her, and was shocked when she revealed that Birch and the Templars were behind the attack on his home. Their father was an Assassin, and Birch had him killed for his secrets. Together, they traveled to Troyes and killed Birch. Haytham returned to the colonies in 1758.