Grandparents and Third Parties: Claiming My Children in Taxes if My Mother Has Guardianship

My question involves a child custody case from the State of: Arkansas my mother has had guardianship of my 3 children due to the fact their father n I both were incarcerated at the same time!! We both signed saying she could have guardianship til we were released n in the papers it says that it's until the absence of the parents is no longer the case!! I've stepped up n taken that role back n she has willingly let them come n stay overnight n at times it's been weeks before we came back by her house!! Only thing I don't have is a documentation from court or anything!! Did she not only void that guardianship when they started staying with me?? But also can I rightfully claim them on my income taxes!!!

Grandparents and Third Parties: Claiming My Children in Taxes if My Mother Has Guardianship