'Descent' in the Bible

He was now approaching the descent from the Mount of Olives. The whole crowd of disciples began to rejoice and to praise God with a loud voice because of all the miracles they had seen.

That is, it is not merely the children born through natural descent who were regarded as God's children, but it is the children born through the promise who were regarded as descendants.

But this man, whose descent is not traced from them, collected a tenth from Abraham and blessed the man who had received the promises.