Unregistered Deposit of title deed mortgage

Contact a local advocate and issue notice to his legal heirs and act as per his guidance.  You may have problems in court fee as you have to seek possession and pay court fee on the market value of the property.  You should take immediate steps either to bind all legal heirs or proceed for recovery of money by filing suit and cautioning public of your interest on the property restraining legal heirs from sale or partition of the property.  Whether such mortgage is legal in your state has also be seen and only local advocate can help you.