We understand that you are overwhelmed and tired of the behaviors your daughter's boyfriend is displaying towards your family. It is important to address this situation with urgency and spiritual wisdom. We stand with you in prayer and offer the following biblical encouragement and advice, but first we want to explicitly explain that this relationship is courtship and not marriage. This relationship should be treated as such and only conducted under supervision and with a specific goal of marriage. If marriage is not imminent, then the couple should go their separate ways.
The Bible tells us to "Be not deceived: evil communications corrupt good manners" (1 Corinthians 15:33 WEB). The behavior of this young man is not only harmful but also influencing your daughter negatively. We must pray for her discernment and strength to resist these influences. It is also good that you are interceding for her to come out of this relationship and for a godly spouse. The more important thing than her having a relationship is the person that she is in the relationship with. You and she both need to trust God will deliver the right spouse.
As a parent you are tasked with training your children. This includes your daughter's boyfriend. Children are told in Ephesians 6:1 to obey their parents in the Lord for this is right. Therefore, fathers do not provoke your children to wrath but bring them up in the training and admonition of the Lord. This young man needs this training and admonition. We agree with you in praying that this young man moves back with his parents, where they can take responsibility for him and provide the guidance he needs. In addition, Proverbs 29:15 says, "The rod and reproof give wisdom, but a child left to himself causes shame to his mother." This young man has been left to himself and has caused shame to his mother, your family, and himself. He is in a state of sin and needs correction.
We also pray for your daughter, that God will grant her wisdom and understanding. The Bible says, "Flee also youthful lusts; but follow righteousness, faith, love, and peace, with those who call on the Lord out of a pure heart" (2 Timothy 2:22 WEB). We pray that she will flee from this unhealthy relationship and pursue righteousness and peace.
Let us pray together:
Dear Heavenly Father,
We come before You in the name of Jesus, lifting up this family that is facing such trial and distress. Lord, we plead the blood of Jesus Christ over them, protecting them from all harm and evil. We pray for Your intervention in this situation, that You would break the chains of this unhealthy relationship and bring peace and healing to this family.
Father, we pray for the young man, that You would convict his heart and lead him to repentance. We pray that he would move back with his parents, and that they would take full responsibility for him, guiding him to become a better person. We pray for him to change his behavior and seek to live in a way that is pleasing to You.
Lord, we also pray for the daughter. Grant her wisdom and discernment to see the truth about this relationship. Help her to resist the negative influences and to flee from this unhealthy bond. We pray for her healing and restoration, that she would find comfort and peace in You alone.
Father, we pray for godly spouses for the daughters, and complete healing for the son with autism. We ask that You would bless this family with a life filled with Your everlasting peace, love, joy, and happiness.
In Jesus' name, we pray. Amen.
We encourage you to continue standing firm in your faith and trusting in the Lord. Remember, "Trust in Yahweh with all your heart, and don’t lean on your own understanding. In all your ways acknowledge him, and he will make your paths straight" (Proverbs 3:5-6 WEB). Keep praying and believing, for with God, all things are possible.
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. 
