There are several verses in which David is promised that his line will always be on the throne of Israel. I want to understand whether this could be extended to adopted children in some cases.
Specifically, for example, 2 Kings 8:19 (WEB):
However Yahweh would not destroy Judah, for David his servant’s sake, as he promised him to give to him a lamp for his children always.
Could the word translated as "children" refer to adopted children also? What is the connotation of this word?
Similarly, Psalm 132:11-12 (WEB):
Yahweh has sworn to David in truth. He will not turn from it:
“I will set the fruit of your body on your throne.
If your children will keep my covenant,
my testimony that I will teach them,
their children also will sit on your throne forever more.”
Here it is clear (at least in English) that the next generation after David will be his biological child ("fruit of your body"), but the subsequent generations are their children which may or may not be biological.
Similarly, 2 Samuel 7:12 (WEB):
When your days are fulfilled, and you sleep with your fathers, I will set up your offspring[a] after you, who will proceed out of your body, and I will establish his kingdom.
"Offspring" there is seed, which is also used in the Greek Scriptures (sperma) such as Romans 1:3. However, even a word like "seek" does not necessarily imply direct biological descent. For example, Romans 9:8 demonstrates that seed is defined more by God's promise than biology.
So, to summarize: would the Hebrew readers of 2 Kings 8:19 understand "children" to be biological children necessarily, or could that be open to adopted children too? Does the Hebrew understanding of adoption allow for this?
Also relevant is this link suggesting that adoption was not a big thing in ancient Hebrew culture.