Why does my left hand or right hand move involuntary when I move the opposite hand like to scratch, pick up something, or any other movement?

My father and I have this thing, no one knows the name of it. When we move one hands fingers or wrists, the opposite hand mimicks the same movements. Sometimes they cramp so bad it hurts. We cannot type normal, always hunt and pick to avoid jamming keys together. If we hold one hand down on the table and wiggle the opposite hands fingers, we can see the fingers and muscles of the other hand moving involuntary all the way up to our elbow. What is this called? One doctor said we are missing coding on our nerves that seperate the left hand from the right hand in the brain. How can I get information on it?