1. Sir my grandma is still alive and what if she denies to give us our share?
2. and i have one sibling, my sister who is married since 2012.
3. what can this case cost to me any idea about it?
If your grandmother is still alive then as per law she is the absolute owner and nobody has any right over the property.
If your uncles have forcibly taken away the possession of property from your grandmother, then only your grandmother has a case against them and not you.
Neither your mother, sister nor you have any rights over the property, especially during the lifetime of the property owner, i.e., your grandmother.
Any litigation you may propose to initiate at this stage may not be maintainable or tenable in law.
Before taking any hasty decision consult a knowledgeable lawyer in the local and proceed as per his advise on all such further issues.