GOD'S WORD® Translation
This means that children born by natural descent [from Abraham] are not necessarily God's children. Instead, children born by the promise are considered Abraham's descendants.

American Standard Version
That is, it is not the children of the flesh that are children of God; but the children of the promise are reckoned for a seed.

Berean Study Bible
So it is not the children of the flesh who are God’s children, but it is the children of the promise who are regarded as offspring.

Douay-Rheims Bible
That is to say, not they that are the children of the flesh, are the children of God; but they, that are the children of the promise, are accounted for the seed.

English Revised Version
That is, it is not the children of the flesh that are children of God; but the children of the promise are reckoned for a seed.

King James Bible
That is, They which are the children of the flesh, these are not the children of God: but the children of the promise are counted for the seed.

World English Bible
That is, it is not the children of the flesh who are children of God, but the children of the promise are counted as a seed.

Young's Literal Translation
that is, the children of the flesh -- these are not children of God; but the children of the promise are reckoned for seed;

Romans 9:8 Additional Translations ...