‘And God remembered Rachel, and God listened to her and opened her womb. And she conceived and bore a son and said, “God has taken away my reproach.” And she called his name Joseph (yoseph), saying, “Yahweh add (yoseph) to me another son.” '
The bearing of children through her handmaid has its own effect on Rachel's body and at last she herself bears a son. Now she feels she can identify herself with Yahweh and His covenant. And in her exultation she looks to Him for more sons. Her words show once again how keenly she had felt her barrenness. It is now seven years since she was first married (Genesis 30:25).
We note in all this the stress laid on the fact the Leah's first four sons and Rachel's first son are from Yahweh Himself. These are the seal of Yahweh's covenant with Jacob. And we note further that there are twelve children. Confederations of twelve are a recognised grouping of tribes in Genesis (Genesis 22:20-24; Genesis 25:12-16) and the fact that Jacob's sons and daughter provide a full tribal confederation does not go unnoticed. He has been truly blessed.
We know from elsewhere the concept of the amphictyony, a grouping of tribes around a central sanctuary, and this was the basis of these tribal federations. We later receive fuller details of such arrangements after the Exodus when Moses formally establishes such a confederation based on association with the twelve sons of Jacob. It should be noted that however the lists of names are changed, there are always twelve names on the list in order to maintain the whole.
But it should be carefully noted that there is no reference to tribal affairs in the comments made on the names of the sons in this passage. They are purely individual. This, together with the inclusion of Dinah to make up the twelve (prior to the birth of Benjamin), is proof of the ancientness of the narrative.