We are truly saddened to hear about the situation with your granddaughter and your son's family. We will stand with you in prayer and seek God's will for this challenging circumstance.
Firstly, we want to address the issue of division within the family. The Bible tells us in Romans 12:18, "If it is possible, as much as it is up to you, be at peace with all men." It is crucial to pursue peace and reconciliation, even in the face of political and faith differences. Remember, our battle is not against flesh and blood, but against the spiritual forces of evil (Ephesians 6:12).
Regarding your son's departure from the faith and his support for stances that do not align with biblical principles, we must remember that God loves everyone and desires that all should come to repentance (2 Peter 3:9). However, it is clear that God calls us to not conform to the pattern of this world, but to be transformed by the renewing of your mind. Then you will be able to test and approve what God's will is—his good, pleasing and perfect will (Romans 12:2). Furthermore, the Bible is clear about sexual immorality and homosexuality. For example, in Leviticus 18:22 it says, Thou shalt not lie with mankind, as with womankind: it is abomination. In Leviticus 20:13 it says, If a man also lie with mankind, as he lieth with a woman, both of them have committed an abomination: they shall surely be put to death; their blood shall be upon them. The Bible also tells us in Corinthians 6:9-10 Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God. Therefore, pray for God to intervene and draw your son and his wife back to Himself, that they may be saved and brought to a knowledge of the truth.
Therefore, pray for God to intervene and draw your son and his wife back to Himself, that they may be saved and brought to a knowledge of the truth. As you have mentioned a belief in demonic influences, put on the full armor of God, so that you can take your stand against the devil's schemes. For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms (Ephesians 6:11-12).
Let us pray together:
Dear Heavenly Father,
We come before You today, lifting up this family in desperate need of Your intervention. Lord, we pray for a supernatural encounter with Jesus for your son, his wife, and their children. We rebuke any spiritual strongholds and demonic influences that may be at work and declare Your sovereignty over their lives.
Father, we ask that You would soften their hearts and draw them back to You. Reveal Yourself to them in a powerful way, that they may know the truth and be saved. Restore unity and peace within this family, and help them to overcome the divisions caused by political and faith differences.
Lord, we also lift up the granddaughter who has not been seen in many months. We pray for a joyful reunion and a strengthening of family bonds. Comfort those who are heartbroken, and give them the strength to endure this trial.
We ask all these things in the mighty name of Jesus Christ, who alone can save and redeem. Amen.
Finally, take heart in the words of Jesus in Matthew 19:26, "With God all things are possible." Trust in the Lord and wait patiently for Him (Psalm 37:7). He is faithful and will hear your prayers.
Prayer Focus: God, Thank You for loving me. God, I ask You in Jesus’ name please bless me with everything that I stand in need of and everything You want me to have. 
