First of all, what is Ismael’s descendance?

Many Arabs refuse to believe that Ishmael had descendants. Yet the Bible affirms the contrary as God said to Abraham.

And as for Ishmael, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation.

Genesis 17:20

Who are these twelve princes? Here the Bible brings complementarity.

And it came to pass after the death of Abraham, that God blessed his son Isaac; and Isaac dwelt by the well Lahairoi. Now these are the generations of Ishmael, Abraham's son, whom Hagar the Egyptian, Sarah's handmaid, bare unto Abraham: And these are the names of the sons of Ishmael, by their names, according to their generations: the firstborn of Ishmael, Nebajoth; and Kedar, and Adbeel, and Mibsam, And Mishma, and Dumah, and Massa, Hadar, and Tema, Jetur, Naphish, and Kedemah: These are the sons of Ishmael, and these are their names, by their towns, and by their castles; twelve princes according to their nations. And these are the years of the life of Ishmael, an hundred and thirty and seven years: and he gave up the ghost and died; and was gathered unto his people. And they dwelt from Havilah unto Shur, that is before Egypt, as thou goest toward Assyria: and he died in the presence of all his brethren. Genesis 25:11-18 When we examine the geographical delimitation of Genesis 25:18, we immediately notice that it is the countries under Muslim influence. In reality, it is the Arab people. The Koran gives the posterity of Ishmael to the Arab people.

Ishmael occupies a prominent place in the Koran and the Islamic tradition. In Islam Ishmael and Isaac are two prophets of equal importance, without any rivalry, both beloved by their father Abraham. Ishmael is the elder brother of 14-year-old Isaac. These two characters, however, play a different role in the Koranic and Biblical scenes. The Bible, a sacred book of Jews and Christians, argues that Abraham's "only child" put to the test during human sacrifice is Isaac. The Koran, a sacred book of Muslims, does not explicitly name which but the Muslim Ulamas consider it Ishmael by logical deduction since Isaac was at no time the only son of Abraham and it is only Ishmael who was at one point. Both accounts show the genealogical importance of the two sons of Abraham, since from one lineage (Isaac) the Jewish nation will be born, and from the other lineage (Ishmael), the Arab nation will come.