We are truly saddened to hear about the struggles you're facing in your marriage and with your family. Let's first bring your requests to the Lord in prayer.
Heavenly Father, we come before You in the name of Jesus, lifting up this beloved sister and her husband. Lord, You have promised that a house divided against itself cannot stand. We pray for unity and understanding between them. Help them to see each other through Your eyes, with love, patience, and kindness.
Father, we also lift up their son and his family. We pray for a spirit of reconciliation, that the walls of separation would be broken down, and that love and forgiveness would flow freely between them. Soften their hearts, Lord, and bring them back into a harmonious relationship.
Lord, we also pray for this sister's husband, that You would touch his heart and release him from any bitterness or hardness. Help him to forgive and to let go of any anger or resentment.
Father, we know that by Jesus' stripes we are healed. We claim divine healing in the name of Jesus. Help her husband to receive the revelation he needs to move forward in faith and love.
Finally, Lord, we pray that Your will be done in their lives, that Your peace would reign in their hearts and home, and that Your love would bind them together. In Jesus' name, we pray. Amen.
Sister, it's wonderful that you acknowledged the power in Jesus' name. Remember what Acts 4:12 WEB says, "There is salvation in none other, for neither is there any other name under heaven, that is given among men, by which we must be saved!" Keep praying and believing in His name.
Regarding your husband, remember what Ephesians 4:31-32 WEB says, "Let all bitterness, wrath, anger, outcry, and slander, be put away from you, with all malice. And be kind to one another, tenderhearted, forgiving each other, just as God also in Christ forgave you." Encourage him to forgive and to let go of the bitterness.
For your son and his family, remember the parable of the prodigal son in Luke 15:11-32 WEB. Keep hoping and praying for their return, and be ready to welcome them with open arms.
Lastly, for your marriage, consider what 1 Corinthians 13:4-7 WEB says about love: "Love is patient, love is kind, it isn't jealous, it doesn't brag, it isn't proud, it isn't arrogant, it doesn't act wrongly, it doesn't seek its own advantage, it isn't provoked, it doesn't keep a record of wrongs, it doesn't rejoice in unrighteousness, but rejoices with the truth. Love bears all things, believes all things, hopes all things, and endures all things." Strive to love each other in this way.
Prayer Focus: God, Thank You for loving me. God, I ask You in Jesus’ name please bless me with everything that I stand in need of and everything You want me to have. 
