Can i legally eligible to take over my dad property?

Hi, i want to have clear solution, I am a first wife son to my dad and having two young sister. My dad got married 18 years ago without knowledge of my mom. Due to her illiteracy she has not find any solution with the family relation member. due to this incident she is in depression now. My dad not at all taking care of his first wife and us. He always giving up cheers to illegal wife and her two female child. He earned more property with the help us during childhood after certain stage he simply leaved us. And, saying that this is my own property you people dont have any share. I asked solution to my relative they also got some money and supporting my dad blackmailing us that, if you legally filing a case we will not support you in future for your life and any function. (They made abortion my baby when my wife pregnancy) due to property rights will go to child based on her(illegal wife) advise 1. Now I want to know can i eligible to file case against him and illegal wife? 2. Can I have all the rights against the property which is on my dad name? kindly help i dont have more money meet them legally if someone help means all three (me and my two sister) will get benefits. At the same times he and she(illegal wife) will go for any extreme level to us for the property attainment. Kindly say clearly