Rights of property

My mother died 4.5yrs back, since then my dad had an intention of getting married again. We are two brothers, both are married and settled in different places. Since dad was alone, I being the younger one was taking care of dad for 2 yrs after my mom's demise. He created all problems between us and moved separately and now he got married. Now the problem is step mom has got 2 unmarried daughters from her 1st husband. My dad has got self acquired property only on his name and not on my mom though the money to buy this property was given by my grandparents. My dad entered into a joint development agreement with the builder and now he has four apartments in his name. My dad has never gone to work. Whatever he has today, it is all my mom's earning, my brother and my earning. After the death of my mom, jewelry was also not distributed between my wife and sister in law. My dad only has it and now step mom is wearing it. How can we claim this. Note. Me and my brother both have 2children. My Dad is still getting my mom's pension. He is aged 72. He has forged his age as 50 and got married. His second wife is aware of his age too. My dad is not ready to give anything to me and my brother. He wants to give everything to his second wife and her daughters.