My brother robbed me and i need legal advise on a promisary?

my brother has robbed me and my insurance wont cover a claim as i let him in my house, he stole 14.5 thousand pounds worth of property and i cannot claim to replace a thing. when our grandad died he left me my house but the inheritance was not enough to cover the mortgage so a promisary was set up and an amount was used from my brothers inheritance to get the house signed over to me. since i cannot claim on my insurance and he is going to crown court for theft and fraud i am wanting to nullify the promisary as means of part compensation for what he stole from me and my children, either that of i will nerver sell my house. whichever way i dont agree with having to give him just under 8k when he has stolen off us what can i do?