My daughter and my son-in-law were married four and half years ago and they have the kids before they were married. The so called mother has not seen them since then. The mother has supervised visitation along with 3 drug test that come back clean, which that has never happened because she don't want to give up her drugs. They are wanting to have her rights taken away. Do they have the right to have her rights taken away.

If your daughter is willing to adopt there is a good chance.

Where? "They" don't have the right to have the mother's rights taken away. This is totally your son-in-law's legal battle as your daughter has no legal standing.

That doesn't change the fact that she is very involved, obviously loves her husband the his children. It's just that this part of the legal process is not hers.