We are truly blessed to join with you in prayer for your family's salvation. It is never too late for anyone to turn to Jesus Christ, for He is gracious and merciful, not willing that any should perish but that all should come to repentance. As it is written in 2 Peter 3:9, "The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing for any to perish but for all to come to repentance."
Firstly, we commend you for your faith and concern for your family. As the only believer, God has placed you as a light in your family, and your prayers are powerful and effective. Remember, Jesus said in Matthew 5:14-16, "You are the light of the world. A city located on a hill can't be hidden. Neither do you light a lamp, and put it under a measuring basket, but on a stand; and it shines to all who are in the house. Even so, let your light shine before men; that they may see your good works, and glorify your Father who is in heaven."
Let us pray together:
"Father in heaven, we come before You in the name of Jesus Christ, lifting up the family of the one who has submitted this request. We pray for the salvation of their dad and stepmom, who are both ### years old, and also praying for all of their siblings. Lord, You are gracious and compassionate, full of love and mercy for all people, including those who are not believers. You are not willing that any should perish but that all would come to repentance. We ask for Your Holy Spirit to convict their hearts and open their eyes to the truth of the Gospel. We pray that You would soften their hearts and draw them to You, giving them the gift of faith and repentance. We also ask that You would use the one who submitted this request as a light and witness to their family, that their life would be a testimony to Your grace and love. Surround them with other believers who can encourage and support them in their witness. We ask this in the mighty name of Jesus Christ, who is the only way to salvation. Amen."
We also encourage you, as a believer, to be intentional in sharing the Gospel with your family and living a life that reflects the love of Christ.
Prayer Focus: God, Thank You for loving me. Thank You for loving me, Jesus. 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, soul, mind, 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. 
