When the LORD accepted Abel's offering but not Cain's, the latter became angry. God warned Cain about potential sin. But even so, Cain murdered Abel. This was the first case of sibling rivalry ... with dire consequences (Gen. 4:4-9).
The reason why Cain killed Abel was sin ... which was portrayed as crouching at the door ready to control the person who opens the door to temptation (Gen. 4: 7). Sibling rivalry is inevitable because all men inherited a corrupt sin nature (Psa. 51: 5). Our sin nature shows up early in life ... young children are capable of experiencing anger and jealousy and may vent their feelings through unkind words and acts. As parents, we have the task of smoothing jealous feelings among our children and promoting sibling harmony.
The second case of sibling rivalry was vividly portrayed by Esau and Jacob in their tussle for the blessing. When Esau heard that Jacob had deceitfully taken his blessing, he burst out bitterly. He held a grudge against Jacob and planned to kill him. When did it all begin? It started when Rebekah overheard Isaac's decision to bless Esau. She then schemed to obtain the blessing for Jacob (Gen. 27:8-10,14-17). But we have to go further back to find the reason for the sibling rivalry.
Rebekah knew that God had chosen Jacob from the beginning (Gen. 25:23). She could have reminded Isaac. She did not. And why did Isaac choose to bless Esau? Did he not know that Jacob was God's choice? Surely, he did ... it was improbable that Rebekah did not tell Isaac that the older (Esau) will serve the younger (Jacob). It might well be that Isaac was present when the LORD told Rebekah of His choice of the younger. How could we account for the separate actions of Rebekah and Isaac?
Rebekah and Isaac were united in marriage but separate in spirit. They were not communicating with one another. Even after the deception, Rebekah was not speaking the truth with Isaac. When Jacob had to flee from Esau's anger, note the reason that Rebekah gave for Jacob's departure ... that she did not wish for Jacob to make the same mistake of marrying a Hittite or Canaanite woman (Gen. 27:46-28:2 c.f. 26:34-35). There was no mention of sibling rivalry ... of Esau's anger, of Jacob's safety and of the danger of Esau becoming a target for blood revenge if he killed Jacob (c.f. 2 Sam. 14:6-7). Rebekah and Isaac were bad models of communication for their two boys.
How parents "fight" or "don't fight" in front of their children communicate important lessons in life about how to treat others. Husband and wife don't agree about everything but we don't have to be unkind towards each other.
The "silent" conflict between Rebekah and Isaac was compounded by parental favouritism (Gen. 25:27-28). Esau was a skilful hunter and could satisfy Isaac's love for wild game. It was natural that Isaac loved Esau more. Jacob was a homely boy ... staying among the tents ... always with his mother. It was natural that Rebekah loved Jacob more. There was a kind of compatibility or matching ... Isaac with Esau; Rebekah with Jacob.
There was nothing wrong with this drawing together of parent and child. What was wrong was that Rebekah and Isaac drew their sons into their conflict. It was a sad day when one parent unites with a child to deceive the other parent. This case of sibling rivalry has its roots in marital disharmony. Some 20 years later and after their parents had passed away, Esau and Jacob had a happy reunion (Gen. 33:4-11).
Jacob (who should know the dangers of parental favouritism) made the mistake of openly showing his favouritism towards Joseph who was born to him in his old age by his favourite wife, Rachel (Gen. 29:30). Benjamin was also born of Rachel and being the younger would be born when Jacob was even older.
Why did Jacob love Joseph more than Benjamin? One possible reason could be that Jacob associated Benjamin with Rachel's death (Gen. 35:16-19). Jacob toiled for seven years to marry the lovely Rachel (Gen. 29:16-20). They waited for a long time before their first child, Joseph was born. It would be unrealistic to expect Jacob not to have special feelings for Joseph (Gen. 37:3). Jacob's mistake was to give Joseph a richly ornamented robe. "And his brothers saw that their father loved him more than all his brothers ..." (Gen. 37:4). In other words, his other sons perceived that as favouritism.
It would be good if Jacob had made all his children feel special in some ways. No two children are the same. Each child is unique. The challenge for parents is to recognise and treasure each child's special qualities and abilities.
Joseph's brothers were jealous of him and would not speak a kind word to him. They called him a dreamer, plotted to kill him, sold him in spite of his pleading, referred to him as "your (Jacob's) son" (Gen. 37:19,26-28,31-32) instead of "our brother." There was no love for Joseph.
The following suggest that Joseph may have played a contributing part in aggravating his brothers' anger and jealousy:
As a result, they hated him even more for his dreams and for his words (Gen. 37:8). The above do not justify the brothers' actions. But it does help parents to remember that it takes two to quarrel.