Which explains these verses:There was another one that mentioned children born of a maidservant. If the father acknowledged them as his sons, they had full rights in paternal inheritance. (Implying that they had no rights to the other wifes inheritance for her children). If he did not acknowledge them as sons, they and their mother were freed upon his death, but no part of the paternal inheritance
Now Abraham gave all that he had to Isaac; but to the sons of his concubines, Abraham gave gifts while he was still living, and sent them away from his son Isaac eastward, to the land of the east.
Genesis 25:5-6 NASB
https://bible.com/bible/100/gen.25.5-6.NASB
Abraham blessed the boys, but Scripture refers to them as 'sons of the concubines' not 'sons of Abraham.'
Now, I need to go back and see how Ishmael is referred to. Because he helped bury Abraham, I assume he is referred to as a son, but because of the promise, he doesn't get the blessing.