Share Of My Dads Property ???

Hello Sir, I had lost my first mother almost about 10 Years ago, and my father decided to get settled again with another lady whom none of us (3 Brothers) consider as mother as she was already married twice or thrice and my dad was her 3rd or 4th Victim. I lost my Dad almost about 4 Years ago. We are 3 brothers and now lady with whom my father lived for 4 to 5 Years also has a daughter. Now this girl has turned 19 and true color of this lady has come out asking for equal share of hers and her daughter from my fathers property which ideally belonged to only us (3 brothers). I being the elder one had looked after both of them after my dad expired and ensured she (Daughter of my dads living partner) is well educated girl. Because of some reasons I am not able to support both the ladies (Second living partner of my expired dad and her daughter) financially now and have stopped sending money to them (Second living partner of my expired dad and her daughter). They have stood up now and approached a local CA / Lawyer who has advised them to file a share. I am not sure whether this second marrige is registered or not, All I want to know are they both (Second living partner of my expired Dad and her daughter) eligible for share in my dads property or can we fight this in court with help of a good lawyer. She is not a nominee in any of my dads property except may be in one or 2 bank accounts which I am sure are closed also now as its been 4 years since he has passed away.