Maria of Brabant, Duchess of Bavaria
Maria of Brabant( 1226–1256) was a daughter of Henry II, Duke of Brabant, and Maria of Swabia.
She married Louis II, Duke of Bavaria, being the first of three wives.
Andronikos Doukas (cousin of Michael VII)
Andronikos Doukas, Latinized as Andronicus Ducas, (died 14 October 1077) was a "protovestiarios" and "protoproedros" of the Byzantine Empire.
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.
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.
Catherine of Bulgaria
Catherine of Bulgaria( Bulgar: Екатерина," Ekaterina"; died after 1059) was Empress- consort to Byzantine emperor Isaac I Komnenos and co-regent of Constantine X for a period after the abdication of her spouse in 1059.
She was a daughter of Ivan Vladislav of Bulgaria and his wife Maria, and thus a sister of Presian and Alusian.
Catherine was also a paternal aunt of Maria of Bulgaria.
Desislava of Bulgaria
Desislava of Bulgaria was daughter of Tsar Ivan Alexander of Bulgaria and his second wife Theodora, a converted Jewish woman.
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).
Maria of Bulgaria, Latin Empress
Maria of Bulgaria was the second Empress consort of Henry of Flanders, Latin Emperor of Constantinople.
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.
Maria of Bulgaria
Maria of Bulgaria (died 21 November, after 1095) was the wife of "protovestiarios" and "domestikos ton scholon" Andronikos Doukas and mother of Empress Irene Doukaina.

Question: What nationality is Maria Of Bulgaria's husband?
Answer: Byzantine Empire