Ala-ud-din Khilji was not a slave before he became a king. He was the nephew as well as the son-in-law of Jalal-ud-Din Khilji. During the reign of Jalal-ud-Din Khilji, Alauddin Khilji was appointed the Governor of Awadh and Kara. However, he wanted to consolidate his position by becoming the ruler of the Khilji dynasty. So, he killed Jalal-ud-Din Khilji, marched to Delhi and proclaimed himself as the king.