The Old Testament sibling rivalries between Cain and Abel, Esau and Jacob, and Joseph and his brothers were similar in some ways and different in others, but they all hold lessons for us today, for brothers today still face many of the same problems in life that challenged brothers thousands of years ago.
Cain and Abel were in a situation much more unique than Esau and Jacob, and Joseph and his brothers faced, for the society they lived in was extremely small, and they each had a direct relationship with God. As the book of Genesis tells us, Cain was the first born son of Adam and Eve. Their next son was a boy whom they named Abel. As Cain and Abel grew up both took responsibilities for making a living. Abel took care of the sheep and Cain became a farmer. (Genesis 4:7).
Both brothers in the space of time began to offer sacrifices unto God. Cain, being a farmer, offered the produce of his fields, and Abel offered the first-born sheep with its fat. God had respect for the offering of Abel but rejected the offering of Cain. Envy of his brother so angered Cain that he killed him.
When God confronted Cain with what he had done and asked, "Where is Abel your brother?" Cain replied, "Am I my brother's keeper?" (Genesis 4:15) The answer is yes, and relates to Esau and Jacob, Joseph and his brothers, and to us today, for we are all our brother's keeper. We live our lives in close relation to our family, neighbors, friends, and even people we only casually meet. We are responsible for how we treat them, and should act towards them as though they were our brothers or sisters.
Another unique element of the Cain and Abel rivalry and its tragic aftermath is that God personally punished Cain for the murder of Abel, and sent him into exile. But God also showed some mercy to Cain which protected him from harm at the hands of others by putting a mark upon him.
The sibling rivalry between Jacob and Esau didn't result from envy due to God's reaction to their sacrifices, but from envy over parental favoritism.