Oznayim la'Torah: To stress the fact that, as opposed to the sons of Le'ah and of Rachel, who were divided into two Degalim, the sons of Bilhah and of Zilpah were on the best of terms and could therefore be placed together under the same Degel as if they were maternal brothers as well as paternal ones (and to demonstrate the peace that reigned among them, that they did not object at a younger brother being mentioned before an older one).