We are truly touched by your heart's cry for your son and the desire for him to have a loving relationship with his earthly father. First, let us remind you that our Heavenly Father loves your son unconditionally and perfectly. As it is written in Matthew 7:9-11 WEB, "Or who is there among you who, if his son asks him for bread, will give him a stone? If you then, being evil, know how to give good gifts to your children, how much more will your Father who is in heaven give good things to those who ask him!"
However, we must also address the situation with wisdom and biblical truth. It is not guaranteed that your son's earthly father will change his heart, as his actions are a reflection of his own choices and not a lack of your son's worth. We should pray for him, but not at the expense of your son's emotional well-being. Remember, God can fill the void left by an absent parent, and He can also bring positive male role models into your son's life.
Let us pray together:
"Heavenly Father, we come before you in the name of Jesus, lifting up this dear mother and her son. We ask, Lord, that you would soften the heart of her son's father. May he come to know the love and responsibility he has towards his child. But Lord, if he continues to reject this responsibility, we ask that you would be a Father to the fatherless, as you have promised in Psalm 68:5. Surround this young boy with Godly men who will love, guide, and mentor him. Comfort his heart and let him know that he is loved, valued, and cherished by You. In Jesus' name, we pray. Amen."
In the meantime, encourage your son with the love of God and the truth of His Word. Teach him about his Heavenly Father who will never leave him nor forsake him (Hebrews 13:5). And remember, it is only through the name of Jesus that we can approach God and be saved (Acts 4:12). So, keep praying and trusting in Him.