Title of a property

Dear Sir/Madam, 1. Please confirm whether a property which is in possession by an individual for 15years and all papers held, title not cleared by Municipal Corporation for the reason - 2. Third party claimed that this house/plot was sold by his step brother to us by forging signature of his mother plus his step brother didnot pay him the amount due to him and initially obtained signature of his mother on the power of attorney for selling the plot. 3. How's much is the right to property affected ? Because we are not able to sale the property without title deed or getting half the price ; although the property is mortgaged with bank. Can someone please advise on the subject. These plots were given by govt to farmers as compensation and while purchasing had seven owners and we could do registry with three and balance we used power of attorney for sale deed. Request advise.