We understand that you are going through a challenging time in your relationship, and we are here to pray with you and provide biblical guidance. Firstly, we want to acknowledge your baptism and the change of heart you've experienced. This is a powerful testimony to the transforming power of the Holy Spirit. However, we want to remind you that it is only by the name of Jesus that we have access to God.
As you face these challenges, remember that God's design for marriage is a lifelong commitment between a man and a woman. It's encouraging to hear that you are considering marriage, as this is the biblical foundation for a family. However, it's crucial to address the issues in your relationship biblically.
Firstly, it's important to address the sexual relationships that led to children outside of marriage. In the Bible, this is considered fornication, but take heart for all have fallen short of the glory of God but the gift of God is eternal life in Christ Jesus our Lord. God wants you to turn away from sin and turn to Him.
Your girlfriend's feelings of hurt, pain, and resentment are valid and need to be addressed. The Bible tells us in Ephesians 4:31-32, Let all bitterness, wrath, anger, outcry, and slander, be put away from you, with all malice. And be kind to one another, tenderhearted, forgiving one another, even as God in Christ forgave you.
It's also important to address the spiritual warfare aspect you mentioned. The Bible tells us in Ephesians 6:12, For we are not fighting against flesh and blood, but against the rulers, against the authorities, against the world powers of this darkness, against the spiritual forces of wickedness in the heavenly places.
Here is our prayer for you:
Dear Heavenly Father,
We come before You today in the name of Jesus, lifting up our brother in his relationship struggles. We thank You for the change of heart he has experienced since his baptism, and we ask for Your continual guidance and strength.
Lord, we pray for his girlfriend, that You would heal her from all the hurt, pain, and resentment she is feeling. We pray that You would give her a spirit of forgiveness, just as You have forgiven us. We pray for their children, that You would protect them and provide for them in every way.
We also pray for our brother, that You would give him the wisdom and discernment to navigate this situation. We pray that he would be a godly example to his girlfriend and their children, and that You would bless their family.
Lastly, we pray against any spiritual attacks on their relationship. We rebuke the enemy in the name of Jesus, and we ask for Your protection and guidance.
In Jesus' name, we pray. Amen.
We encourage you to continue praying together as a couple, seeking God's will for your relationship. Remember that God can heal and restore any situation, no matter how broken it may seem. Trust in Him, and He will guide you.
Lastly, we want to encourage you to consider pre-marital counseling with a pastor or a trusted Christian mentor. This can provide a safe space to address these issues and prepare for a godly marriage. Keep your eyes fixed on Jesus, and He will guide your paths.
Prayer Focus: God, Thank You. Thank You for loving me. God, I ask You in Jesus’ name bless me with everything that I stand in need of and everything You want me to have. Bless me to know You in truth, fall in love with You with all my heart, mind, soul, body, and strength and never fall out of love with You. Bless me to have an ever growing closer stronger, more intimate relationship with You. Bless me with the love, desire, strength, and the spirit of obedience to always delight myself in You, seek first Your kingdom, and Your righteousness. Help and strengthen me God to always respect and obey You. Bless me to trust You with all my heart, acknowledge You in all my ways, and lean not to my own understanding. 
