Fraudulent Step Mother

My father married a woman discreetly ( it could also be that she blackmailed him to marry her as no one from our family knew about it), I lost my mother 20 years back. The woman he has married now has intentions to grab the property. She is a divorcee with two children. Her daughter is married and son stays with her ex husband. How can I safeguard the property. My father is willing to make the documents required so she does not get any share in the property. Recently there was also a family settlement between my father and his brother. He also has received some properties in Hiba ( Gift deed ) from his mother ( my grandmother). Also does the gift deed mean that the property is on his name? Is family settlement also regarded as property in my father’s name? It says for few properties that my father and his bother “shaamilat hisse mein rahenge”. My father is ready to give me a gift deed. Can he also gift deed based in family settlement documents? What are her children’s (not from my father, from her ex husband) rights in my father’s property? Is Hiba document a registered property document?