Looking at 2 sets of brothers, Isaac & Ishmael and Jacob & Esau, we learn from this dysfunctional family about what needs to happen for reconciliation to take place.
Abraham's faith is put to the test when God asks him to sacrifice Isaac on the same mountain where Jesus was later crucified. In this we see a glorious foreshadowing of Jesus.
Ishmael and Hagar are sent away in a story that is at the same time historical and allegorical, speaking to us about the battle between the flesh and the spirit.