To Shem also, the father of all the children of Eber, the elder brother of Japheth, children were born. The sons of Shem: Elam, Asshur, Arpachshad, Lud, and Aram. The sons of Aram: Uz, Hul, Gether, and Mash. Arpachshad fathered Shelah; and Shelah fathered Eber. To Eber were born two sons: the name of the one was Peleg, for in his days the earth was divided, and his brother's name was Joktan. Joktan fathered Almodad, Sheleph, Hazarmaveth, Jerah, Hadoram, Uzal, Diklah, Obal, Abimael, Sheba, Ophir, Havilah, and Jobab; all these were the sons of Joktan. The territory in which they lived extended from Mesha in the direction of Sephar to the hill country of the east. These are the sons of Shem, by their clans, their languages, their lands, and their nations.
These are the clans of the sons of Noah, according to their genealogies, in their nations, and from these the nations spread abroad on the earth after the flood. – Genesis 10:21-32
Usually the right of the firstborn is to be listed first in the genealogy. Here the example with Cain is followed (Gen 4:17-26). The focus in the early writings of Israel’s history is to focus on the seed is promise last. So also here, Shem and his line are highlighted as the line of promise and blessing by God. It is Shem’s line that will receive extra attention after the story of Babel (Gen 11:10-32) in much the way as Seth (Gen 5:4-32).