I think one of the most despicable acts that parents can commit is to play favorites with their children. In one of the first families we see favoritism by the parents (Isaac loved Esau and Rebekah loved Jacob), and the result was one brother pitted against the other.
In a moment of physical weakness, Esau traded what was very precious to him (his birthright) for a temporary fulfillment of his immediate appetite. In that day and age, the oldest son received a double portion of his father’s inheritance, and that double portion was known as a birthright. It’s interesting that after Esau gives up his birthright he despises it. Isn’t it funny the way we despise things that reveal our weaknesses or our poor decisions?