John Calvin Commentary Genesis 10:21

"And unto Shem, the father of all the children of Eber, the elder brother of Japheth, to him also were children born." — Genesis 10:21 (ASV)

Unto Shem also, the father of all the children of Eber. Moses, being about to speak of the sons of Shem, makes a brief introduction, which he had not done for the others. Nor was it without reason; for since this was the race chosen by God, he wished to sever it from other nations by some special mark.

This also is the reason why he expressly styles him the father of the sons of Eber, and the elder brother of Japheth. For the benediction of Shem does not descend to all his grandchildren indiscriminately, but remains in one family. And although the grandchildren of Eber themselves declined from the true worship of God, so that the Lord might justly have disinherited them; yet the benediction was not extinguished, but only buried for a season, until Abraham was called, in honor of whom this singular dignity is ascribed to the race and name of Eber.

For the same cause, mention is made of Japheth, in order that the promise may be confirmed: God shall speak gently unto Japheth, that he may dwell in the tents of Shem. Shem is not here called the brother of Ham, inasmuch as the latter was cut off from the fraternal order, and was debarred from his own right.

Fraternity remained only between them and Japheth; because, although they were separated, God had promised that he would cause them to return from this dissension into union. As it respects the name Eber, those who deny it to be a proper name, but deduce it from the word which signifies to pass over, are more than sufficiently refuted by this passage alone.