In Exodus, God instructs Moses to tell Pharaoh that Israel is his "firstborn"
Exodus 4:22-23 (NWT)
And you must say to Phar′aoh, ‘This is what Jehovah has said: “Israel is my son, my firstborn. And I say to you: Send my son away that he may serve me. But should you refuse to send him away, here I am killing your son, your firstborn.”
This implies that there are additional "children" Who are the other children and how many other "sons" were placed on the earth?