Title: Isaac II Angelos
Content:  Isaac II Angelos (Ἰσαάκιος Κομνηνός Ἄγγελος; September 1156 – January 1204) was Byzantine Emperor from 1185 to 1195, and again from 1203 to 1204. His father Andronikos Doukas Angelos was a military leader in Asia Minor (c. 1122 – aft. 1185) who married Euphrosyne Kastamonitissa (c. 1125 – aft. 1195). Andronikos Doukas Angelos was the son of Constantine Angelos and Theodora Komnene (b. 15 January 1096/1097), the youngest daughter of Emperor Alexios I Komnenos and Irene Doukaina. Thus Isaac was a member of the extended imperial clan of the Komnenoi.
Title: Isaac II Angelos
Content: Anna-Euphrosyne Angelina, married to Roman the Great. ; Irene Angelina (c. 1181-1208), married first to Roger III of Sicily and secondly to Philip of Swabia. Isaac is the ancestor of all European monarchs now reigning through Irene's children by Philip. ; Alexios IV Angelos (c. 1182 - 1204). Manuel Angelos (b. after 1195 – d. 1212), he was evidently the elder son, being contemplated in 1205 to ascend the Byzantine throne ; John Angelos (b. ca. 1193 – d. 1259). He migrated to Hungary and ruled over Syrmia and Bacs (1227–42) as a vassal of king Béla IV of Hungary. 
Title: Angelos
Content:  Constantine's third son Andronikos Doukas Angelos, was the progenitor of the imperial Angelos dynasty. In 1185, Andronikos' son Isaac II Angelos deposed Andronikos I Komnenos and was proclaimed Byzantine Emperor. Irene Angelina, a daughter of Isaac II Angelos, married Philip of Swabia, King of the Germans. Their daughters married into a number of western European royal and princely families. Many of the extant aristocratic families of Europe are, therefore, descendants of the Angeloi. Isaac was deposed by his brother Alexios III Angelos, who was in turn overthrown by Alexios IV Angelos with the aid of the Fourth Crusade. Under the corrupt and dissolute reign of the Angelos dynasty, the Byzantine empire deteriorated and soon fell prey to Latin crusaders and Venetians in the Fourth Crusade.
Title: Angelo Flavio Comneno
Content:  The Angeli claimed to be direct male-line descendants of Emperor Isaac II Angelos ((r. undefined – undefined)1185–1195 and 1203–1204), whom they also claimed was a direct descendant of Constantine the Great ((r. undefined – undefined)306–337). Giovanni Andrea I Angeli (1569–1634) claimed Isaac II was his ancestor in the ninth degree. Although Isaac II had many descendants in the female line, being related to many noble and royal houses in Europe through his daughter Irene Angelina, and had sons, any direct male-line descendants were long dead before the Angeli arrived in Italy. The male line of the Angelos emperors is not recorded to have survived beyond the death of Emperor 
Title: Angelus Family
Content: Isaac II Angelos ; Alexios III Angelos ; Alexios IV Angelos Angelus Family may refer to: 
Title: Andronikos Doukas Angelos
Content:  wife and offspring are unknown. ; Isaac II Angelos (1156–1204), in 1183 he led a rebellion along with Theodore Kantakouzenos against AndronikosI at Nicaea, but after Kantakouzenos' death submitted to the Emperor. Isaac's killing of the hated chief minister, Stephen Hagiochristophorites, in 1185 inspired a popular revolt that deposed Andronikos and brought Isaac to the throne. He ruled until deposed by his brother Alexios in 1195, but was restored by the Crusaders in 1203, remaining on the throne along with his son Alexios IV until his death, shortly before the final Sack of Constantinople by the Crusaders. He married first an unknown lady and had three children, Anna-Euphrosyne, Irene, and AlexiosIV; with his second wife, Margaret of 
Title: John Angelos of Syrmia
Content:  John Angelos was the son of Isaac II Angelos, the Byzantine Emperor from 1185 to 1195, and again from 1203 to 1204; and Margaret of Hungary, the daughter of King Béla III (r. 1172–1196) and sister of King Emeric (r. 1196–1204). John had three older half-siblings from his father's first marriage: Anna-Euphrosyne, Irene Angelina and Alexios IV Angelos, while he had a younger full brother, Manuel Angelos (b. after 1195 – d. 1212). The family found refuge in the Hungarian court in 1222. King Andrew II of Hungary (r. 1205–1235), his uncle, gave him "Syrmia and beyond", i.e. south of the Sava river, including Belgrade and Macsó, which he ruled until 1253. In 1221, Pope Honorius III demanded that the "heretics" (Bogomils) be exterminated in Bosnia. His chaplain Aconcio was unable to gain any followers in Ragusa, 
Title: Alexios III Angelos
Content:  Alexios III Angelos was the second son of Andronikos Doukas Angelos and Euphrosyne Kastamonitissa. Andronikos was himself a son of Theodora Komnene, the youngest daughter of Emperor Alexios I Komnenos and Irene Doukaina. Thus Alexios Angelos was a member of the extended imperial family. Together with his father and brothers, Alexios had conspired against Emperor Andronikos I Komnenos (c. 1183), and thus he spent several years in exile in Muslim courts, including that of Saladin. His younger brother Isaac was threatened with execution under orders of Andronikos I, their first-cousin once-removed, on 11 September 1185. Isaac made a desperate attack on the imperial agents and soon killed their leader Stephen Hagiochristophorites. He then took refuge in the church of Hagia Sophia and from there appealed to the populace. His actions provoked a riot, which resulted in the deposition of Andronikos I and the proclamation of Isaac as Emperor. Alexios was now closer to the imperial throne than ever before.
Title: Angelos
Content:  The Angelos family, feminine form Angelina (Ἀγγελίνα), plural Angeloi (Ἄγγελοι), was a Byzantine Greek noble lineage which rose to prominence through the marriage of its founder, Constantine Angelos, with Theodora Komnene, the youngest daughter of Emperor Alexios I Komnenos. As imperial relatives, the Angeloi held various high titles and military commands under Emperor Manuel I Komnenos. In 1185, following a revolt against Andronikos I Komnenos, Isaac II Angelos rose to the throne, the first of three Angeloi emperors who ruled until 1204. The period was marked by the decline and fragmentation of the Byzantine Empire, culminating in its dissolution by the Fourth Crusade in 1204. After the Fourth Crusade, another branch of the family managed to establish an independent state in Epirus. The members of this branch largely eschewed the use of the 
Title: Byzantine Empire under the Angelos dynasty
Content:  Meanwhile, in Constantinople, the deposed Isaac II Angelos and his son Alexios IV Angelos were both in prison following the coup of Alexius III Angelos. However, Isaac was not destined to spend the rest of his days in jail; his young son Alexios IV escaped prison in the summer of 1203 and fled to the court of Philip of Swabia, the younger son of Frederick I Barbarossa. Philip and Alexius IV were brothers-in-law due to the former's marriage to the later's sister, Irene Angelina. Alexios appealed to Philip to help him and his father regains the Byzantine throne. Fortunately for Alexios IV, Phillip had good connections with the new leader of the Fourth Crusade, Boniface I of Montferrat (Theobald 

Question: Who is the father of Isaac II Angelos?
Answer: Andronikos Doukas Angelos.