God Has No Grandchildren
First century Jews, who were hypocrites, thieves, liars and extortionists, often claimed to be "children of God" Jn. 8:41. To this the Lord responded; "If God were your Father, ye would love Me… And because I tell you the truth, ye believe me not" vs. 42 and 47. To John the Baptizer, they likewise identified themselves as "Children of Abraham" or "Abraham's seed" Jn. 8:33, 39. To which John objected; "that God is able of these stones to raise up children unto Abraham" Lk. 3:8 &Matt. 3:9.
Those Jews obstinately attempted to legitimize their relationship with God through the ancestral pedigree. But, both John and the Lord repudiated such vanity.
"He came unto his own, and his own received Him not. But as many as received Him, to them gave He power to become the sons of God, even to them that believe on His name: Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God." Jn. 1:11-13
Paul expressed his earnest desire for Israel to believe and obey the gospel of Christ, affirming that mere physical ancestry is inadequate Rom. 9:3-6. Even Ishmael and Esau were descendants of Abraham. But, the children of the "promise" Rom. 9:9-13 are legitimate children of God.
Amazingly today, many mistakenly base their entire relationship with Almighty God upon that of their family heritage instead of the very own personal submission, and obedient faith in Jesus Christ. "For ye are all the children of God through [the] faith in Christ Jesus. For as many of you as have been baptized into Christ have put on Christ. There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus. And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise." Gal. 3:26-29