This situation prompted Uroš I to search for support among the Hungarians which resulted in the first marital connections of and Serbian dynasties with the ruling dynasties of Europe. Helena, daughter of Uroš I, married Hungarian king Béla II. She was proposed for Béla, then an heir apparent, by his uncle and predecessor Stephen II in 1129. After Béla II succeeded to the throne in 1131, Helena became de facto ruler, as he was blinded as a child. She organized reprisals and mass executions of the magnates who participated in Béla's blinding. She also extended her rule during the regency and initial ruling years of her son Géza II. Her two other sons also later became kings of Hungary: Ladislaus II and Stephen IV. Helena's brother, Beloš, also established himself in Hungary, becoming a palatine, co-regent of Hungary (1141–1146) and ban of Croatia (1142–1158 and 1163). Beloš married his daughter to Vladimir III Mstislavich, later a Grand Prince of Kiev. Uroš II married his second daughter, Marija, to Conrad II of Znojmo, a Bohemian prince, where she became known as Mary of Serbia. Two remaining children of Uroš I, sons Uroš II and Desa remained in Serbia and participated in the political life. Hungarian-backed politics of Uroš I prevented Byzantines to fully occupy and dismantle Raška as they did in Duklja for a while. During the rule of Uroš I, a meddling of the ruling dynasties of Raška and Duklja into each other affairs continued, though they descended from the same lineage.