Share of o common law wife who falsified public documents (ie TCT's)

Good day! I would like to seek your help regarding our current dilemna in the family. I am a legitimate child born out of legally married parents but eventually got a legal separation decades ago. My father "remarried" and i have 2 half-siblings with his common law wife. Our dad passed away about a year ago and his properties are now our bone of contention. My question is that is my dad's 2nd wife entitled half of his estate considering the following factors: 1) as the informant of one of my half sibling's BC, she declared her as legitimate when she clearly is not 2). All other titles bearing our dad's name reflects "Juan dela Cruz MARRIED to Maria dela Cruz" 3) titles which are supposed to be hers alone reflects the surname of my dad instead of her maiden name. The problem is she wants to get all of the properties left by my dad for herself and her children and maintains that she is entitled to 50% of the properties while the other 50% should be divided between my & my 2 half siblings (1 share to their 1/2 each) Since there has been a premise of falsification on their part, can i file a case against her for the said offense? Can I contest her 50% share considering that she has no means of income to purchase these properties? What i wanted was equal sharing amongst all of us but she has other plans which is quite disheartening.

Thanks so much for our help!

did your parents really have a legal separation? what happened to their properties based on the court's judgment? is your mother still alive?

Yes they did have a legal separation po. Yes, my mother is still alive. I will have to ask their lawyer for a copy of the legal separation docs po. Thank you, attorney!