Muslim Personal Law regarding property rights for wife of second marriage.

Good day! I am writing this letter on behalf of my friend. He is an Indian citizen(Muslim).He has one sister who is married and settled in Muscat. After 3 years of the death of his mother, his father remarried to a financially poor lady under pressure of his relatives. Even the marriage was not informed to my friend or his only sibling. Later when they know about that there where some verbal fights. My friend and his sister were very mush ashamed in their locale area and up to 6 years they don't take a look at their father due to what he did. Later on when he become the age of marriage he need to sort out every issues in his family before entering into a family life. As a part a panel including friends and family approached him and as a result long sittings we made the family rejoined again. But the second wife doesn't like the presence of her husband's children. She started delivering wrong comments and unfair practices towards them. Even she took the 63 year old man to an unauthorized infertility center for getting pregnant from him. Consuming the medicines from the clinic his health also become weak and her intention was unsuccessful. Medical team predicted a cardiac arrest if he did this practice again. The lady already removed the names of my friend and his sister from the ration card. Now she is trying to remove them from Masjid Mahal membership. As per the words from my friends father,she is also compelling him to give land properties to my friend and sister and change the ownership of the house which they stays to his name. Which literally means making the children away from their father and even she said."Whatever he can give you,he will give you. Later on no one should enter into this premises saying this is my father". My friend is afraid of the life of his father,once if he did the above it can even be harmful to his life. I need a clear picture in the regards below. 1) What is the legal rights which a second wife can have from her husband as per Muslim Personal Law in India? 2) Doesn't the children from his first marriage have any rights on their father and his belongings? 3) What is the property right of second wife without children?