Help drug rehab in Texas? Please help

I am looking for advice for a nephew of mine and don’t know what to do. First of all, I want to start by saying we are not a bad family. I am a teacher, my sisters are teachers, and my only brother is a rancher. We are a normal middle class family with hardworking parents and just trying to be good people. However, my brother’s oldest son has always had issues with depression and socially awkward. My brother is now raising my nephews children because he and his wife were not taking care of the kids like they should have. We now suspect my nephew is on meth because he isn’t eating, we think he hasn’t eaten in over a week. My mother lets my nephew and his wife stay in one of her rent houses. Well he called my mom over a few days ago and assured her someone is living in the attic. My mom looked and found nothing. He also thinks there are cameras in his car and people are watching him. His eyes are dilated too. We have never dealt with anything like this before. We are clueless on what to do. My nephew is about 27 so I don’t think we can force him into rehab. I am just looking for guidance on what we can do. Please if anyone has family members that have been through this or you have become clean tell us how we can help. I’m so afraid he is doing these horrible drugs and we are going to find him dead some day.