It is not easy to get custody of the grandchildren from their parents. The law is that if she leaves the children with you then that is not abandonment. You can refuse to take them. You can call CPS if you feel that they are in danger,unless CPS gets involved there is not alot you can do. You might want to ask her to give you consent to file for guardianship,if she will then you can file for the legal guardianship. The only other option for you is to keep an eye on the situration and report anything that you are concerned about to CPS,if it involves the kids welfare. Wish there was more you could do. You can call an attorney and see what they sujest,but it is pretty standard to have to get the parents consent. Watch that the children have know bruises,check them if you feel the boy friend is spanking them. Marks are a sign of abuse.