leaving me out of my share illegally

My elder sister died on 2014 without any Wasiyatnama, we r survived by me( brother) my second sister and my mother, deceased sister nominated my mother and soon after my second sister with connivance from the other 7 members of a housing co-operative in Rajarhat, cheated my mother and took an undertaking from her and my second sister has turned into a full owner of the under constructed building, I was never notifiednotified whatsoever and I feel betrayed, my mother had no sense in doing that out of ignorance, what is my next step to claim my share of 55.5% as per Islamic inheritance lawlaw. Plz help me