The pirate-turned-Assassin Edward Kenway returned to England with his young daughter Jennifer in tow. Upon receiving a pardon from Lord Robert Walpole, he moved to London in order to work with the Assassins there.
Once there, he met Tessa Stevenson-Oakley, the daughter of his landlord. Using her family connections, Tessa helped Edward purchase a manor in Queen Anne's Square. They were married soon after and had a son, Haytham. The Kenways weren't like other well-to-do London families and they were a frequent subject of gossip.
Edward was rarely seen, often travelling about the city, and Europe, on mysterious business. Haytham was schooled inside the mansion, and rarely allowed to speak to anyone outside its walls. There was but one frequent visitor to the house, Edward's business associate Reginald Birch, who began to court Jennifer, much to her dismay.
Jennifer knew the truth about her father's past, and when she discovered that Birch was a Templar who was after his secrets, she tried to warn him. Birch sent mercenaries to the Kenway Mansion. Edward was killed and Jennifer was sold to Turkish slavers.
Oblivious to the truth, Tessa Kenway allowed Birch to become Haytham's legal guardian and take him away, while she remained in London to oversee repairs to the mansion. She died alone twelve years later, allegedly from a fall.
Years passed, and Haytham, now a Templar trained by Birch, found Jennifer in Damascus. The siblings confronted Birch in Troyes, France, and killed him. Jennifer returned to London and took possession of the mansion in Queen Anne's Square. Although she and Haytham kept in touch, she was a bit bitter that her brother chose to remain a Templar, despite learning of Birch's treachery. She became quite the recluse; her only visitor of note was a young Elise de la Serre, who was visiting London on something of a soul-searching trip.
Out of respect for Haytham Kenway's accomplishments, the Templars made no attempt to claim the property while Jennifer was alive, despite their beliefs that there were many Assassin secrets still hidden inside it. After Jennifer's passing in 1805, the Order quietly purchased the lot. It's not known what, if anything, any of the Kenways hid there, and even its location remained a mystery to the Assassins for many years.