Does she and the kids live with you or someone?  Probably someone (like you) can claim her and the kids as dependents.  Or is the father claiming the kids?  Is she married?

My son gets SSI and I am also his caretaker

Please start a new post. You have commented on an old post that has already been answered.

If your daughter has no income other than SSI for her son, there is no need to file a tax return and she would not get any kind of refund or credit from filing one.