I do not believe this is possible. It is not like you go to an office, sit down with the devil and sign an agreement. If you did, how could you trust the devil anyway? It sounds like you are desperate, but thousands of others are also suffering. God is not responsible for our suffering, though we sometimes may wonder why He does not stop certain things from happening. Also, the devil does not have any power over God so calling on him will not change your family situation, and is likely to make it worse. You should NEVER invite the devil into your life, even if you think your intentions are good. He preys are the weak, the lonely and the depressed in order to cause damage. If your family is suffering, it does not need any more of this. I truly hope you come out of your despair and your family survives whatever is ailing them.