We understand your concern for your sister-in-law and brother, and we are here to pray and provide biblical guidance with you. It's important to remember that the love of worldly things can lead us away from God, as it is written in 1 John 2:15-17 WEB:
"Do not love the world, neither the things that are in the world. If anyone loves the world, the Father’s love is not in him. For all that is in the world, the lust of the flesh, the lust of the eyes, and the pride of life, is not the Father’s, but is the world’s. The world is passing away with its lusts, but he who does God’s will remains forever."
Let us pray together for your family:
"Father in heaven, we come before You in the name of Jesus Christ to lift up our ### and ###. We ask that You forgive them for any wrongdoings they may have committed and that You remind them that You are the only way to true peace and happiness. We pray that You will help them to overcome any obstacles in their lives and that You will teach them to seek after the things of God rather than the things of this world.
Lord, we ask that You draw them closer to You and that You will fill their hearts with a desire to serve You and to love You above all. We know that You are capable of changing even the hardest of hearts and that You want nothing more than to see them come to You.
We ask that You will strengthen their marriage and allow them to find a deeper love for each other as they walk with You. We rebuke any idolatry in their lives and pray that you will teach them to love You above all else.
We pray all these things in the precious name of Jesus Christ, who gave Himself for our sins, that He might deliver us out of this evil world, according to the will of our God and Father. Amen."
We encourage you to continue praying for them and to share the gospel with them, reminding them that true peace and happiness can only be found in Jesus Christ. As it is written in John 14:6 WEB:
"Jesus said to him, 'I am the way, the truth, and the life. No one comes to the Father, except through me.'"
Remember to speak the truth in love, as it is written in Ephesians 4:15 WEB:
"But speaking truth in love, we may grow up in all things into him, who is the head, Christ."
We are standing with you in prayer, trusting that God will work in their hearts and draw them to Him.