Is my father in law cousin brother child demand for half property

Hi I am postiong question on behalf of my father in law(A). He had purchased property in 1991 in delhi at that time his cousin brother (B) also was living with him at delhi.(B) has been died in 2001 there after my father in law helped his family as they had not source of income . (B) wife requested my father in law please take my younger child (Y)with him to delhi.So my fahter in law brought him in delhi and helped him to get job.But after (Y) got married he also brought his wife to delhi and enjoy all the facilities free.As my father is living alone in delhi so he did not resist.But this year he asked them to vacant my home as I have transfer it to my daughter and want to leave delhi.But they refused to do that and ask for half property, (Y) always abused my father in law and she involved some local ladies with their help she try to put false blame on him.Police also not helping too much as these ladies have some powerful connection.Please tell whether (Y) can claim half of the property as he has driving licence a fake ration card only.