Bible, John 3:16:
(CJB) “For God so loved the world that he gave his only and unique Son, so that everyone who trusts in him may have eternal life, instead of being utterly destroyed.”
(ISV) “For this is how God loved the world: He gave his uniquely existing Son so that everyone who believes in him would not be lost but have eternal life.”
I think the word “unique” here should read “having universal property” (as universal properties defined in mathematics, specifically category theory).
There are many children of God, but they are children of God only through “universal” son of God that is Christ.