'Born' in the Bible

concerning His Son, who was born of a descendant of David according to the flesh,

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.

(For the children being not yet born, neither having done any good or evil, that the purpose of God according to election might stand, not of works, but of him that calleth;)