Tracing Tennants

Hi guys I need some advice. We gave a property for rent way back in the 70s'. The person we gave it to went into a partnership with another person. Our orginal tennant died so the partnership passed onto his wife. We have been trying to evict them ever since. Because we were living abroad the case was lost each time. I am now settled here i have been trying to get my property back. I have no idea where my orginal tennats wife lives. WE are not receving any rent. Any papers we try to serve at our property are returned to the advocate. Now I want to know whether my advocate is playing silly beggars and screwing me or are papers normally returned like this. I would also like to know how to go about finding my tennant. I have no address of her or her relatives. Thanks Any advice will be gratefully received. The last rent recevied was Rs75 per month. The property next door which is smaller than ours gets Rs3000 per day. So you can see why I am anxious to get this sorted. I am based in Kerala (not sure if this makes any difference.