Are the (other) sons of Abraham though Hagar & Keturah considered Abraham's seed...?

“Furthermore, Abraham again took a wife,” Keturah, and thereafter fathered six additional sons, so that from Abraham sprang not only the Israelites, Ishmaelites, and Edomites but also Medanites, Midianites, and others. (Ge 25:1, 2; 1Ch 1:28, 32, 34) Thus it was that Jehovah’s prophetic utterance was fulfilled in Abraham: “A father of a crowd of nations I will make you.” (Ge 17:5) Finally, at the good old age of 175, Abraham died, in 1843 B.C.E., and was buried by his sons Isaac and Ishmael in the cave of Machpelah. (Ge 25:7-10) Prior to his death Abraham gave gifts to the sons of his secondary wives and sent them away, so that Isaac would be the sole heir of “everything he had.”—Ge 25:5, 6.