I have had my grandchild living with me for 3 years and I have custody through a noterized statement from her mom but I want to file for full custody as we ( grandparents ) are providing all of her support. Can I legally get custody?
My daughter has some mental issues and may be pregnant for a 3rd time and it is not a good environment for the 3 yr. old.

The notarized statement has no weight of law. A court must grant custody. You should be able to get guardianship at least.

No you have no custody except the fact they live there, the notarized statement is not a legal document for custody, Notarized only means it was witnessed and that they made sure who signed it. Since it did not go thought he court and get approved by the judge, it is not a legal custody order at all. So while you can use that in court to show they intended you to watch the children for you. You will need to get the mother and father sign over their rights to allow you to have custody and have this done though the courts.

As long as they do not object and sign the paper work you should have no trouble. Now they may not like having to pay chld support to you, once you are given custody.

I would not try for custody. Custody implies a more permanent legal bound and may be harder to get. I would go for legal guardianship.

In either case, you should get an attorney to make sure its done legally and the attorney can advise the best way to go.