Minority Registration & Gift deed cancellation

We have purchased a plot at main road near railway crossing Bobbili, in 2005 in the name of m my mother. After that we left that town for my father's job. Recently when we went to see our plot, found a building in construction for a 2 wheeler show room. Immediately we have checked EC which is still in my mother's name. We went to the builder and asked him, he also claiming that the land belongs to him, showing his registered documents. After checking them we found that both of our plot no's are same but the layout is different, but as our plot is good for commercial use so only he is intentionally claiming for himself. But his neighbouring boundaries are different from that of actual site. How we have proceed now? As we both have bought plots from the brothers who has laid different layouts with same plot no's. We would like to solve this issue legally. Any body can please guide us?