Individual Details

Birth

Upon Pope Innocent III's request, the ecclesiastic and temporal dignitaries of the Kingdom of Hungary took an oath before his birth that they would accept him as his father's successor.
The infant Béla was probably present when a group of conspirators murdered his mother on 28 September 1213. Following the murder, his father ordered only the execution of the conspirators' leader and forgave the other members of the group, which resulted in Béla's emerging antipathy against his father.
In the beginning of 1214, Béla was engaged to a daughter of Tzar Boril of Bulgaria. Shortly afterwards, he was crowned junior king. When his father left for a Crusade in August 1217, his maternal uncle, Archbishop Berthold of Kalocsa took Béla to the fortress of Steyr in Styria and he returned to Hungary one year later, following his father's return from the Holy Land.

Death

Béla lost his favourite son in the summer of 1269. Afterwards, his favourite daughter, Anna exercised more and more influence over him. In his last will, Béla entrusted his daughter and his followers to her son-in-law, King Otakar II of Bohemia, because he did not trust his son.

Marriage

Her parents wanted their daughters to all make important political marriages, which would create alliances for Duke Berthold IV. Gertrude married the Árpád prince Andrew II, younger son of late King Béla III of Hungary, before 1203. Andrew thereby took sides in the conflict over the German throne, joining his father-in-law in his support of Duke Philip of Swabia, while his elder brother King Emeric of Hungary backed King Otto IV of Germany. The couple had five children:
Anna Maria of Hungary (c. 1204 – 1237), wife of Tzar Ivan Asen II of Bulgaria
King Béla IV of Hungary (1206 – 3 May 1270)
Saint Elisabeth of Hungary (1207 – 10 November 1231), wife of Landgraf Louis IV of Thuringia
King Coloman of Galicia-Lodomeria (1208 – June 1241)
Prince Andrew II of Halych (c. 1210 – 1234)
Ambitious Gertrude exerted much political influence over her husband. It was probably she who persuaded Andrew to conspire against his brother again, but when King Emeric, who had realised that Andrew's troops outnumbered his armies, went unarmed, wearing only the crown and the sceptre, to Andrew's camp near Varasd, Andrew surrendered voluntarily on the spur of the scene. The king had his brother arrested, but Andrew managed to escape shortly afterwards. During this time, Gertrude was sent back to her father. Things improved for her, when Prince Andrew took over the government of the Hungarian kingdom upon the death of King Emeric in 1204, officially as regent for his minor nephew Ladislaus III, who nevertheless died driven in exile one year later.