Sons were also born to Shem. Shem was Japheth's younger brother. All of the sons of Eber came from Shem.
References for Genesis 10:21
The sons of Shem were Elam, Asshur, Arphaxad, Lud and Aram.
The sons of Aram were Uz, Hul, Gether and Meshech.
Arphaxad was the father of Shelah. Shelah was the father of Eber.
Eber was the father of two sons. One was named Peleg. That's because the earth was divided up in his time. His brother was named Joktan.
Joktan was the father of Almodad, Sheleph, Hazarmaveth and Jerah.
He was also the father of Hadoram, Uzal, Diklah,
Obal, Abimael, Sheba,
Ophir, Havilah and Jobab. All of them were sons of Joktan.
The area where they lived stretched from Mesha toward Sephar. It was in the eastern hill country.
Those are the sons of Shem. They are listed by their tribes and languages in their territories and nations.
Those are the tribes of Noah's sons. They are listed by their family lines within their nations. From them the nations spread out over the earth after the flood.