We are truly saddened to hear about the situation your daughter and her family are facing. Let's bring this before the Lord in prayer and seek His guidance and intervention.
Firstly, we need to acknowledge that the behavior of your daughter's son is not aligning with biblical principles. The Bible tells us to honor our parents (Ephesians 6:2) and to live in harmony with one another (Romans 12:16). It is clear that he is allowing anger and violence to control him which cannot be allowed to continue. His actions are sinful and harmful to everyone involved.
In this situation the Bible is clear:
Ephesians 5:29 WEB "For no man ever hated his own flesh; but nourishes and cherishes it, even as the Lord also does the assembly"
1 Timothy 5:8 WEB "But if anyone doesn’t provide for his own, and especially his own household, he has denied the faith, and is worse than an unbeliever."
1 Timothy 5:4 WEB "But if any widow has children or grandchildren, let them learn first to show piety towards their own family, and to repay their parents, for this is acceptable in the sight of God."
We also need to address that the cause of this behavior is not aligned with biblical principles as well. He is distraught and violent due to a breakup with his girlfriend. This is an indication that he may be involved in an intimate relationship outside of marriage, which the Bible warns against. Sexual relations outside of marriage is considered fornication which is sinful. 1 Corinthians 6:18 WEB "Flee sexual immorality! 'Every sin that a man does is outside the body,' but he who commits sexual immorality sins against his own body." We need to pray for him to turn away from this sin and turn to God.
Let's pray:
Dear Heavenly Father,
We come before You in the name of Jesus, lifting up our sister and her family. Lord, we ask for Your divine intervention in this situation. We pray for Your protection over them and for Your wisdom to guide them.
We pray for your daughter's son. Lord, we ask that You soften his heart and bring him to repentance. Help him to see the error of his ways and turn away from his sinful behavior. We pray that he would seek Your face and find peace in You alone, not in a relationship with his girlfriend. We also pray for his healing, both physically and spiritually. We ask that You would surround him with godly influences and bring him to a place of surrender to Your will.
We also pray for your daughter and her family. Lord, we ask that You would give them strength and courage in this trial. Help them to forgive as You have forgiven us, and to love as You have loved us. We pray that You would heal their hearts and restore their family.
We pray that the name of Jesus Christ be invoked in all matters and that salvation is sought through Him alone. If they have not done so, convict their hearts, in Jesus name.
Finally, we pray for the girlfriend. We ask that You would minister to her heart and bring her to a place of repentance as well. We pray that You would work in her life and bring her to a saving knowledge of You.
In Jesus' name, we pray. Amen.