You mean a Veteran's Affairs divorce decree? Contact the VA in your area. Its usually a 1-800 number. You can talk to a rep, they can access anything by you social. If you had it done by legal on base there will be a record of it. If it was done off base at your duty station then you will have to contact the city/county courthouse where the divorce was granted. I have never heard of a VA divorce decree, I worked for the VA about 10 years ago so maybe things have changed, but try both of those things.
I have no idea and am not in the field of law. But I don’t think Judges are in the habit of placing children with parents who may not be able to care for the child because of additions.
If the father never hit the child, he may get custody because he has done nothing that would have his parental rights removed from him.
Also, I don’t know if the judge would place the children with the mother’s parent if both parents are not fit to have parental right. They may be places with qualified foster care parents while the grandparents are being investigated to see if they are an adequate placement.
Also, the father’s parents would have just as much rights as the mother’s parents.
Even if your mother doesn’t ask the court for mandatory drug rehab for your sister, I am sure that the father of the child will bring it up in court so the drug issue is going to work against her either way. She should show she is already enrolled and getting treatment BEFORE she enters the courtroom. This could be the only thing that could save her custodial right. Also, perhaps if she were living with her parents while she was going through her rehab program, the courts could see that there are responsible adults in the home and that the child’s needs are being met when he is in his mother’s care.
That is just my best guess. I am not really qualified to speak on this subject though, so you may want to seek professional help from someone in the field.