This passage seems to assign lesser importance to the four sons that Jacob had with the handmaidens of Leah and Rachel. However, the Zohar reveals that the spiritual system and supernal structure of reality is perfect, complete, and includes all components, no matter how irrelevant they might appear. Though the four children are not present among the Sfirot, they are included in the symbolic body of Adam Kadmon as the joints of his arms and legs.
A good computer system depends on a powerful microprocessor. If a tiny, "insignificant" wire is absent or defective, the entire system is rendered inoperable. All the elements are, in a manner of speaking, equally important. Similarly, everyone in this world is as important as the most righteous sage, including those we might consider to be on a lower level of spirituality than ourselves. It behooves us to stop judging others, and to recognize that every person plays a vital role in the spiritual structure of humanity. This passage instills this wisdom in our consciousness, so that we may begin living it every day.