In total, Abraham had eight sons born to three different women. His firstborn was Ishmael, whose mother was an Egyptian slave girl, Hagar. Abraham's second son, Isaac, was delivered by his first wife Sarah, while he had another six sons with his second wife, Keturah.
There is some confusion as to how many sons Abraham had, as the Bible appears to contradict itself. In Galatians 4:22, it talks about Abraham having two sons, referring to Ishmael and Isaac. However, in Genesis 25:1-2, it mentions that Abraham remarried after his first wife Sarah had died. With his second wife Keturah, Abraham also had sons called Zimran, Jokshan, Medan, Midian, Ishbak and Shuah. These latter sons are not mentioned further because they are not central to Abraham's story.