She has no share in property standing in your joint names 

but she can stay in property owned by your father 

Grandson has no share in father or grand father self acquired property 

If she is filing a DV case seeking residential rights, then it becomes the duty of her husband to provide accommodation to her as per law provided she still remains his legally wedded wife then, in whatever circumstances, she cannot claim residential rights in the property owned by you or your father if your brother is not the part of that household. 

There is no concept of ancestral property in Muslim personal law.

Even otherwise the grandfather's property cannot be ancestral property to the grandchildren, if the grandfather is not living then the properties left behind by him shall devolve on his sons and not on his grandchildren, therefore your fears are imaginary 

1. There's no legal right for her to stay in the property owned by you and your father. However it's upto you and your father to allow her to stay in the property.

2. Your brother's wife shall not have any legal right over the property owned by you and your father.

3.  During your father's lifetime, her son, who is 5 yrs old, will not have any share in your father's property.

Yes, if she gets an order from court in a proceeding under PWDV Act then you could not evict her anymore from that place.

So better get this vacated before she moves to court. 

Under the said Act she does not become its owner but her right of residence therein can not be hampered by you anymore. 

Dear Client,

In the Present Scenario, your brother's wife and her parents are staying in a property that is owned by you and your father. However, your mother is still alive. Your brother is still processing a divorce as they have an issue. Your question here is that, whether she is allowed to stay in the property or does she have a right on the property owned by you and your father. Herein, since the property has been owned by you and your father, your brother's wife usually would not have a legal right unless there are any specific agreements to that effect. With respect to divorce, while your brother's wife may not have rights in the property per se, the court may consider her situation to provide maintenance or any such arrangements to that effect. However, if you wish that she leaves, you may provide a formal notice as well for her eviction. But it is suggested that firstly, you have a conversation with your brother's wife, on her intentions and looking into the divorce proceedings.

Hope you find this answer beneficial for resolving the dispute.

- As per law , your wife is having residential right from you , but not from your parents/father. 

- Since, the property is jointly owned by you and father , then your father can evict them from his property legally. 

- Further, your wife and the son have no right over your and your fathers property during your life time.