Right and Left

Kol HaTor Chapter 2 part 1

151 - ... And our Rabbi already explained the first thought of Yosef's brothers; they knew that when Avraham's soul came down to this world, the Klipah of the Right Side attached to him, and therefore Yishmael came out from him in order to separate him from the Klipah. And when the soul of Yitzchak came to the world, the Klipah of the Left attached to him, and therefore Esav came from him in order to separate him from the Klipah. And they (Yosef's brothers) thought that the Klipah of the Middle had attached itself to Yaakov, who is of the Middle Line, and after they saw Yosef act with traits of arrogance, they thought for sure Yosef was of the Klipah that had left Yaakov, and they didn't know of his holiness and Yosef's great role in the preparation for the Geulah.

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We see from this that Avraham Avinu, from the Right Side (the side of Chesed) was essentially perfected by the birth of Yishmael. It removed the Klipah from him. Avraham became personally complete at age 86.

Likewise, Yitzchak, who was from the Left Side (the side of Din) was brought closer to perfection by the birth of Yaakov and Esav at age 60, since Esav was the Klipah that was attached to Yitzchak. This was only completed, however, with the transfer of the Bechorah (firstborn status) to Yaakov 15 years later at the age of 75. As Rashi comments on Breishit 27:36, Yitzchak's conversation with Esav. Yitzchak realizes that it was proper for him to bless Yaakov, as he was the bechor (firstborn), and that he was going to bless Esav because he thought incorrectly that he was the bechor.

The Tikkun that took place through the birth of Yishmael and Esav is what allowed Yaakov to not have any Klipah attached to him. Only when the Left and the Right become perfected, they can then join together to form the Middle.