If there are class 1 legal heirs including your father/mother you can not take any property unless through process of law. The details provided is inadequate and you can not expect a meaningful guidance unless you inform facts like the Class 1 legal heirs, who is in possession and enjoyment, death of your grandfather or Class 1 legal heirs etc. Contact a local advocate with all relevant documents. This issue is not such simple that can be acted upon through forum guidance, whereas several facts and documents have to be studied.
You have not stated the material facts. Anyhow, there is no question of taking belonging to another person. It is only that you seek your share if you are a joint holder in any property by operation of law.