We understand your concern for your friends, Alfutha, and we'll address this situation with care and biblical truth.
Firstly, we must address the issue of sexual immorality. The Bible is clear about God's design for marriage and sexual intimacy. It should be between one man and one woman within the confines of marriage (Hebrews 13:4, WEB). Any deviation from this is sin. In the case of Justine, her involvement with Stephanie is indeed wrong and sinful. As it is written, "You shall not lie with a male as with a woman. It is an abomination." (Leviticus 18:22, WEB) and "Likewise also the men, leaving the natural use of the woman, burned in their lust toward one another, men doing what is inappropriate with other men, and receiving in themselves the due penalty of their error." (Romans 1:27, WEB)
Moreover, their living arrangement is also a concern. They are living together as if married, but they are not. This is fornication, which is also sinful (1 Corinthians 6:9, WEB). The fact that they are planning to move Stephanie back in, given Justine's involvement with her, will only exacerbate the situation.
As for the children, they deserve to be raised in a stable, godly home. This environment is confusing and not aligned with biblical principles.
Let's pray for them:
*Dear Heavenly Father, we come before you in the name of Jesus Christ, lifting up Mike, Justine, Stephanie, and their children. Lord, we pray that you convict Justine and Stephanie of their sin and draw them to repentance. Help Mike to stand firm as the spiritual leader of his home, guided by your word. We pray for their children, that they may be protected and grow in the knowledge of you. Most importantly, Lord, we pray that they all come to the saving knowledge of Jesus Christ if they haven't already. In Jesus' name, we pray. Amen.*
Alfutha, it's crucial to share these truths with them in love (Ephesians 4:15, WEB). Encourage them to seek God's will for their lives. If they are unsure of their standing with God, remind them that "if you will confess with your mouth that Jesus is Lord, and believe in your heart that God raised him from the dead, you will be saved." (Romans 10:9, WEB)
May God grant you wisdom, courage, and love as you minister to them.