1. It is essential to know the nature of the suit, It must be or should be a ' suit for declaration of your share and injunction'.
2. The relatives of the other co-sharers can transfer their share in favour of a third party and on this basis alone their deed will not be cancelled.
3. However such deed is not binding on you since your grand mother has not transferred her share in the name of that third party.
3. Now the said 3rd party has got 3/5th share in the property and you can not dispute this fact.
4. So you can either sell your balance share to him or buy his share from him.
5. if you have in possession of the property then you are in better position to negotiate.
6. If you are not satisfied with your current lawyer you can change him with another one.