'Children' in the Bible

The Spirit Himself testifies together with our spirit that we are God’s children,

and if children, also heirs—heirs of God and coheirs with Christ—seeing that we suffer with Him so that we may also be glorified with Him.

that the creation itself will also be set free from the bondage of corruption into the glorious freedom of God’s children.

Neither are they all children because they are Abraham’s descendants. On the contrary, your offspring will be traced through Isaac.

That is, it is not the children by physical descent who are God’s children, but the children of the promise are considered to be the offspring.