They came along at about the same time.
Abraham The father of Isaac was also the father of Ishmeal.
These two half bothers families have been fighting since Ishmeal and his mother Hagar where forced from their home by Abrham's wife Sarah. She, Sarah, didn't want her slave and her new son around when Isaac was born.
This "jealousy" started a rivalry that may never end.
Isaac is the father of all Jews. Ishmeal is the father of all Arabs. It is simply a family quarrel.
Then there was also the way the Jews treated everyone they encountered when they were freed from Egypt. They often killed every living thing in their path and their acts have not been forgotten.
P.S. I am a Christian, but I find it ironic that we all worship the same creator. Even this make some extremist very made. Even the act of calling upon God by the name that they refer to him as can get you murdered in many places in the world.
That is the short of it, but Ishmeal was born first.