Asen dynasty
Unnamed Asen sister„mother of Boril and Strez”
An unnamed sister of the first three Asens — Ivan I Asen, Peter and Kaloyan — and mother of tsar Boril and the sebastokrator Strez. The link through which Boril and Strez belong to the imperial house.
Biography
An unnamed sister of the first three Asens — Ivan Asen I, Peter and Kaloyan. The sources have preserved neither her name nor any detail of her life; she is known solely as the mother of Tsar Boril and of Sevastokrator Strez.
Through her, her sons belonged to the royal line: it was on the maternal side that Boril, a nephew of Kaloyan, justified his claim to the throne after his uncle's death in 1207, and on the same line Strez too was reckoned a member of the house of Asen.
Sources
“Сестра на Иван I Асен, Петър и Калоян; майка на Борил и Стрез.”
— Genealogy and Prosopography of the Asen Dynasty 1186–1460, p. 69