What does the Bible teach about God's family?
The Bible teaches that only true believers have been given the right to become children of God. Believers are adopted into the family of God through faith.
In Adam, all humanity fell. Consequently, all are born in sin and are enemies of God. Sin makes us children of wrath deserving condemnation and eternal separation from God. But through faith (trust) in the work of Jesus, the enemies of God are reconciled to him and made his children!
Yet to all who did receive him, to those who believed in his name, he gave the right to become children of God.
What does Mormonism teach about God's family?
Mormonism teaches that all people are the literal spirit children of God. They are the product of Heavenly Father and Heavenly Mother. Satan and his demons are also literal children of God who rebelled and were cast out.
Man, as a spirit, was begotten and born of heavenly parents, and reared to maturity in the eternal mansions of the Father, prior to coming upon the earth in a temporal [physical] body.
Teachings of Presidents of the Church: Joseph F. Smith 
Have you ever felt unprepared to share your faith?
Our free booklet explores a variety of helpful methods and themes to prepare you to share the truth in love.
Why this Matters
Mormonism's teaching about God's family seems comforting at first, but it minimizes the sacrifice and work of Jesus. The gift of God's grace in favor is diminished.
Trust in Jesus and his completed work is what makes one a child of God. Those who do not trust Christ and Christ alone are not God's children but rather are God's enemies who will be eternally separated from him in hell.
Hearing that we were not born as children of God is frightening. But when we dig a little deeper to understand how God makes people his children, we find lasting comfort. We were his enemies, but God lavished his love upon us by adopting us as his children and making us righteous through faith in the finished work of Jesus. God calls those who trust in Jesus "sons" and "daughters" and declares them to be heirs of eternal life with him.
Only believers have been given the right to become children of God.
All people are the literal spirit children of God.