We are truly saddened to hear about the trials your family is currently facing, and we are here to intercede and lift you up in prayer together.
Firstly in all things we should pray in the name of Jesus. It is only by His name that we can approach God the Father and ask for His will in prayer. God is sovereign over all things including pain and infections. He uses them for His good and His glory. That does not mean that we cannot pray for healing. We should pray for healing, but we should pray for God's will and understand that His will is always best.
Let's pray for your son's ankle, asking God to relieve the pain and restore his ability to walk. We find assurance in James 5:14-15 (WEB), "Is any among you sick? Let him call for the elders of the assembly, and let them pray over him, anointing him with oil in the name of the Lord, and the prayer of faith will heal him who is sick, and the Lord will raise him up. If he has committed sins, he will be forgiven."
Regarding your husband and his family, we pray for God's comfort and strength to envelop them during this difficult time. We know that God is close to the brokenhearted and saves those who are crushed in spirit Psalm 34:18 (WEB). We also pray for your mother-in-law, asking God to intervene and heal her if it is His will. But what is most important is that she believes in Jesus. We know that physical healing in this life is temporary, but healing from sin and eternal life in Jesus is forever. In this life we are called to share the gospel and proclaim Jesus as Lord and Savior. Jesus is the great physician and healer of our souls. As it says in Acts 4:12 (WEB), "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!" Let us pray that your mother-in-law, your husband, you, and all in your family believe in Jesus if you do not already. We also pray for peace and strength for your husband as he goes through this trial.
In all things we should praise God for our trials. Consider it pure joy when you face trials of many kinds. That is what James 1:2-4 (WEB) says. We also know that And we know that God works all things together for the good of those who love him, who have been called according to his purpose Romans 8:28 (WEB).
Father, we come before you in Jesus' name, seeking your will for this family. We pray for healing for their son's ankle, and we ask for your divine intervention in the life of your husband's mother. If it is your will, Lord, heal her physically, but most importantly heal her soul if she does not believe in Jesus. We pray for your comfort and strength to surround your husband and his family during this time. We ask that you use this trial to draw them closer to you. We pray for healing of your family's souls if they do not believe in Jesus, and we pray that through this trial you use it to make your family stronger believers in Jesus. Help them to trust in your sovereignty and goodness, even in the midst of pain and suffering. In Jesus' name, we pray. Amen.
Lastly, we encourage you to remain steadfast in faith and trust in God's unfailing love and goodness. Cast all your anxieties on him, because he cares for you 1 Peter 5:7 (WEB). As a family, cling to God's promises and seek His will in all things.