Themes in Genesis: The Older Serves the Younger - Birth Order

One common theme throughout Genesis is the younger son becoming more important than the older one. This theme is repeated over and over.

1. Cain killed his older brother Abel and then Seth was born who was became the most important one in the family.
2. Abraham gave his blessing to Isaac who was his second born because his first born Ishmael was the son of an Egyptian slave who was expelled from the house by his wife Sarah.
3. Isaac's son Jacob stole the blessing and bargained for the birthright from his brother Esau.
4. Jacob's son Reuben lost his birthright and blessing to Judah (4th in line) because of his affair with his step-mother.
5. Judah's son Er was given Tamar as his wife. Er died so Tamar was given to Er's brother Onan who also died. Finally, she tricked her father-ion-law to have sex with her so she could have a child, but instead of having one child she bore twins, Pharez and Zarah. As Zarah was coming out of the womb a red thread was tied around his hand to identify the first born but he was pulled back into the womb by his brother who then came out first.
6. When Jacob blessed his children he also blessed 2 of his grandchildren, Manasseh and Ephraim, who were sons of Joseph. When Jacob placed his hands on the 2 children he put his right hand on the younger child thus giving the best blessing to the younger of the two. Joseph tried to correct his father, but Jacob refused to change his hands' position. The younger was to be the greater of the two.

So what's the issue with the older serving the younger theme? Perhaps the writer of Genesis was a younger brother.