Question: When was the sister of Theodora Porphyrogenita died who was reigned as Byzantine Empress alongside her sister?
Sentence (from "Theodora Porphyrogenita (11th century)"): Theodora Porphyrogenita (Greek: Θεοδώρα, "Theodōra" ; AD 980 – 31 August 1056) was a Byzantine Empress born into the Macedonian dynasty that had ruled the Byzantine Empire for almost two hundred years.
Relevant evidence: Yes