Legal rights of a child born out of wedlock

I and my brother were born to my parents out of wedlock. My father was already married and had 2 kids before getting into a relationship with my mother. Their marriage was not solemnized either in a social gathering or in the court of law as his first wife was still alive. From childhood, I have always seen bitter relationship between my parents. My father used to visit us whenever he wants and many a times, it would be months gap between his visits. They used to fight on all possible things and he used to leave the next day and return only after weeks and months. His support was minimal to zero in terms of both social and financial needs. We were not introduced to his side of the family; we haven't seen our grand parents as well. As we grew, questions from the society about his whereabouts, why he doesn't stay with us etc.. used to bite us. To get a glimpse of him, talk to him and request him to stay with us, myself and my brother used to visit his place of business and his home and plead him to stay with us also sometimes. We were abused by his first wife and son multiple times and while our father would talk to us when he sees us there but it would be as though he was speaking to someone else's children. He never disclosed that we were his children to public. His first wife and children knew about us though. My mother took care of us by teaching kids. As we grew up - attained 15 years of age, we started working while educating ourselves. We stopped visiting him at his shop and home as he would treat us with disrespect. Irrespective of all this ill treatment from him, my mother still accepted him anytime he used to visit us and expected us to respect him as a father and we obliged. He was involved in every decision making at home, our marriage and everything while getting no support from him financially except for the fact that he would act like our father. Though he lives in the same city, we don't know where he stays or what he does for his living as we stopped to follow him. Things started becoming worse after my mother was diagnosed with brain stroke. Post 2 years of this event, he started pressurizing us to sell property on my mother's name which was bought in 1998 after selling a piece of land again on my mother's name. My mother initially resisted to sell the property and later agreed as my father started fighting for it every time he visits us. Photo copies of the documents were given to him and he started to deal with interested buyers and without letting us know he took money from them and entered an agreement as well and then started to deny registration, demanding more money from the buyers. I got involved and solved it. The issue now is, he wants money or sale proceedings saying the property is his own and for name sake he got it registered on my mother's name. In fact, he is claiming share in my mother's ancestral property as well. I wish to know what would be his rights on these properties.