Cecilia was a minor character seen in Underworld: Evolution. She appeared only in flashbacks. She was the sister of Selene, and maternal aunt to Eve. Her name was only mentioned in the second novelization; in the end credits of Evolution, she was simply credited as "Selene's Sister".
Cecilia was born to a Hungarian family sometime in the late 1300s. Her father was a well-known Master Mason-&-Smith who was commissioned by a Vampire Elder, Viktor, to build a prison. The fortress was a dungeon intended for the imprisonment of the Werewolf William Corvinus, who was condemned for his bloody and destructive behaviour.
As children, Cecilia and Selene had roamed the halls of the dungeon, and even painted on one of its walls. In 1396, Cecilia gave birth to twin girls.
Six years later, in 1402, an uprising of Lycans at the Vampire stronghold led to the escape of Lucian, the Lycan leader who desired revenge on the Vampires due to the murder of his lover, Sonja. Before fleeing the Vampires' castle, Lucian had stolen Sonja's pendant, which served as one half of the key into William's lair. Realizing the consequences that could come should Lucian ever find William's prison, Viktor tracked down all of the builders and murdered them one by one.
That same winter, Viktor, along with two other Vampires, Kraven and Soren, attacked the household of Cecilia and her family: Cecilia died inside the house, her screams awakened Selene. Immediately after, her entire family was slaughtered, with the exception of Selene, who was made a Vampire by Viktor. The father of Cecilia’s daughters apparently did not live with Selene’s family at the time of the attack, as he was never mentioned when Selene recounted the story later.
Due to the deaths of her family, Selene spent the next 600 years tracking and killing Lycans, whom she believed were responsible for their slaughter.