We are truly saddened to hear about the situation you're facing, and we're here to intercede and help you navigate this trial in a way that honors God. Firstly, let's bring your family and the situation before the Lord in prayer.
Father in heaven, we come before you in the name of Jesus, lifting up our sister and her family. Lord, you know the situation they're in, the financial struggles, and the misplaced priorities. We ask that you forgive them for putting money and material things above you. Help them to see the error and repent. Give them the strength to turn away from greed and turn to you.
Lord, we know that the love of money is a root of all kinds of evil, and in their pursuit of wealth, they have pierced themselves through with many sorrows. We ask that you deliver them from this.
Father, we pray for wisdom and guidance. Show them what to do, guide their footsteps, and give them a spirit of discernment. Help them to trust in you, not in uncertain riches.
Lastly, we pray that through this trial, they would seek first the Kingdom of God and his righteousness, and all these things would be added to them. In Jesus' name, we pray. Amen.
Now, let's look at what the Bible says about this situation.
For the love of money is a root of all kinds of evil. Some have been led astray from the faith in their greed, and have pierced themselves through with many sorrows. But you, man of God, flee these things, and follow after righteousness, godliness, faith, love, patience, and gentleness. (1 Timothy 6:10-11 WEB)
But seek first God's Kingdom, and his righteousness; and all these things will be given to you as well. (Matthew 6:33 WEB)
It's clear that the pursuit of wealth has led your family astray. But there's hope. God is willing and able to forgive and restore, if they turn to him.
You mentioned that they claim to make money hand over fist in the stock market, but they've lost a lot of money. This reminds us of the parable of the rich fool in Luke 12:16-21. The man was rich, but his life didn't consist of the abundance of his possessions. He wasn't rich towards God.
We encourage you to share these verses with your family, and pray that God would open their hearts to receive his word.
Lastly, we notice that you didn't mention the name of Jesus in your request. It's important to remember that it's only by the name of Jesus that we have access to God. As it's written in John 14:6, Jesus said to him, "I am the way, the truth, and the life. No one comes to the Father, except through me." And in Acts 4:12, neither is there salvation in any other, for there is no other name under heaven that is given among men, by which we must be saved."
If you haven't already, we encourage you to put your faith in Jesus Christ, and to encourage your family to do the same. It's only through a relationship with him that we can truly have peace and hope, both in this life and the next. There is no other name by which we are saved.
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. 
