Knut stated in a letter to Pope Clement III that his bride was the only one who was of sufficiently high status to marry him, which may point to royal connections.
This in turn can be compared with a genealogy that mentions Ubbe (Ulf), Kol and Burislev as the sons of Johan Sverkersson.
To avoid death, the Queen promised on her sick bed, that if God would spare her life, she would enter a convent after her recovery to show her gratitude.
Knut argued that he must secure the support of her relatives in order to fight the pagans east of the Baltic Sea, and therefore maintain married life.
After Erik's death, Karl Sverkersson from the rival House of Sverker succeeded him, forcing Knut into exile, while Cecilia was placed in a convent for her safety.
Their marriage took place after Knut ascended the throne in 1167, but it was temporarily dissolved when Cecilia was again compelled to enter a convent in the 1190s due to an illness (see above).
While her existence is not firmly established, it is somewhat accepted in scholarly literature as an explanation for Knut Magnusson's hereditary claim to the throne.
She is also proposed by old romanticized genealogies as mother of a Duke's daughter Cecilia Knutsdotter (by necessity born near 1208 at earliest), whose parentage however is fully shrouded in mists of history.