Complex sentence: Alfonso VII of Castile (March 1,1104/5--August 21,1157), nicknamed "the Emperor", was the king of Castile and Leon since 1126, son of Urraca of Castile and Count Raymond of Burgundy.
Split into simpler sentences: Alfonso VII of Castile (March 1,1104/5--August 21,1157), nicknamed "the Emperor", became the king of Castile and Leon in 1126. He was the son of Urraca of Castile and Count Raymond of Burgundy.