Before starting my question, I assume there might be several mistakes in my "knowledge" of Islam so apologies in advance.
If I understand correctly, according to the jewish and muslim traditions, muslims are the descendants of Ishmael son of Abraham and jewishs are the descendants of Isaac son of Abraham. Later in the story, jewishs were expecting a Christ or Messiah, a king that will bring salvation to jewishs and mankind. Christians believe the christ to be Jesus and they also believe him to be the son of god, jewishs believe it wasnt Jesus, and muslims believe the christ was Isa (Jesus) but he wasnt the son of god.
My question is, why muslims incorporate this part of the story of jewishs (the christ) which has nothing to do with muslims? (since muslims are the descendants of Ishmael who wasnt an ancestor of Christ, so this part of the story isnt connected at all with muslims ancestors) . I dont understand this because if muslims believe the ultimate word of god was revealed to them, then why they think god kept a link only with jewishs about Christ, sending jewishs the Christ.