Maria Palaiologina Kantakouzene
Maria Palaiologina Kantakouzene  was a Byzantine princess, niece of emperor Michael VIII Palaiologos, and empress consort of Constantine Tikh of Bulgaria and Ivaylo of Bulgaria.
She is the most powerful Empress of Bulgaria, ruling as a regent from 1271 to 1279.
Anna Maria of Hungary
Anna Maria of Hungary (1204–1237) was an Empress consort of Bulgaria, daughter of King Andrew II of Hungary and Gertrude of Merania.
She was sister of Saint Elizabeth of Hungary.
In January 1221 she married Tsar Ivan Asen II of Bulgaria as his second wife.
Her father was forced to agree to the marriage to effect his release from Bulgaria, where he had been captured on his return from Crusade in late 1218.
Her dowry included the cities of Beograd and Braničevo.
Anna Maria and Ivan Asen II had several children, including:
She died of the plague in 1237 and was buried at SS.
Forty Martyrs Church in Tarnovo.
Elena Asenina of Bulgaria
Elena of Bulgaria was an empress consort of Nicaea, married to Theodore II Laskaris (r. 1254–1258).
She was daughter of Bulgarian Emperor Ivan Asen II and Anna Maria of Hungary.
Kiril, Prince of Preslav
Prince Kyril of Bulgaria, Prince of Preslav (Kyril Heinrich Franz Ludwig Anton Karl Philipp; 17 November 1895 – 1 February 1945) was the second son of Ferdinand I of Bulgaria and his first wife Marie Louise of Bourbon-Parma.
He was a younger brother of Boris III of Bulgaria and a prince regent of the Kingdom of Bulgaria from 1943 to 1944.
Lamman Rucker
Lamman Rucker( born October 6, 1971) is an American actor.
Rucker began his career on the daytime soap operas" As the World Turns" and" All My Children", before roles in Tyler Perry's films
" Why Did I Get Married?
Why Did I Get Married Too?", and" Meet the Browns", and its television adaptation.
In 2016, he began starring as Jacob Greenleaf in the Oprah Winfrey Network drama series," Greenleaf".
Desislava of Bulgaria
Desislava of Bulgaria was daughter of Tsar Ivan Alexander of Bulgaria and his second wife Theodora, a converted Jewish woman.
Keratsa of Bulgaria
Keratsa-Maria of Bulgaria( 1348–1390) was Princess of Bulgaria during the Second Bulgarian Empire and Empress of Byzantine Empire.
She was the daughter of Tsar Ivan Alexander of Bulgaria and his second wife, a converted Jew, Theodora.
Ana-Neda
Ana- Neda( Bulgarian and; fl. 1323- 1324) was the Empress consort of Bulgaria briefly in 1323- 1324 as the spouse of" Despot of Vidin" Michael Shishman who was elected as Emperor of Bulgaria in 1323.
She was the daughter of Serbian King Stefan Uroš II Milutin and Princess Ana Terter, daughter of George I of Bulgaria.
From the marriage with Michael, they had three sons, one of whom was Ivan Stephen of Bulgaria, later briefly the Emperor of Bulgaria( 1330 – 1331).
Irene Komnene Doukaina
Irene Komnene Doukaina or Eirene Komnene Doukaina was an Empress of Bulgaria during the Second Bulgarian Empire and Byzantine princess.
She was the third wife of tsar Ivan Asen II of Bulgaria.
She was the mother of tsar Michael Asen I of Bulgaria.
Maria Asenina of Bulgaria
Maria Asenina of Bulgaria was a Bulgarian princess and empress consort.
She was the consort of Emperor Mitso Asen of Bulgaria( reigned 1256 – 1257).
She was the daughter of Emperor Ivan Asen II of Bulgaria and Empress Irene Komnene of Epirus.
Through her mother, she was a granddaughter of Theodore of Epirus.
She is mother of Bulgarian Emperor Ivan Asen III( r. 1279 – 1280) and of Bulgarian Empress Kira Maria, who married Emperor George I of Bulgaria.

Question: What is the cause of death of Elena Asenina Of Bulgaria's mother?
Answer: plague