Vacant of house from my daughter in law who has remarried

I am 64 year old. I live with my husband and kids. One of my son did suicide due to pressure from his wife and her family members. Now its been 4 years since i have lost my son. She is living here in my house with my grandson. She does not even take care of him. She hardly sends him school for 2 days in a week. Yesterday i got to know that she has remarried and she is living here just for property. I have met her new husband also. But now she has refused that she is not married and she will not even give my grandson. How should I proceed to get my house vacant as well as my grandson's custody when his mother does not take care of him. There are so many such incidents where step fathers kill their step kid. How should I get my house vacant. Please help. Me and my husband are really very tensed.