Jesus himself answered this question, in John 8. Jesus is speaking directly to the Jewish religious leaders of the time. He petty much states not only are they, not Abrahams's children which to me, means offspring, but he also states that God is not their father!! the devil is !!!
John 8
39“.Abraham is our father,” they replied.
“If you were children of Abraham,” said Jesus, “you would do the works of Abraham.
40. But now you are trying to kill Me, a man who has told you the truth that I heard from God. Abraham never did such a thing.
41. You are doing the works of your father.”
“We are not illegitimate children,” they declared. “Our only Father is God Himself.”
42. Jesus said to them, “If God were your Father, you would love Me, for I have come here from God. I have not come on My own, but He sent Me.
43.
Why do you not understand what I am saying? It is because you are unable to accept My message.
44. You belong to your father, the devil, and you want to carry out his desires. He was a murderer from the beginning, refusing to uphold the truth because there is no truth in him. When he lies, he speaks his native language,
because he is a liar and the father of lies.
45. But because I speak the truth, you do not believe Me!