Can a grandparent claim a grandchild that did not live with her all year. Custodial parent has no income, other parent pays child support. Grdparent provides support

Children live with custodial parent which only income is child support and food stamps. The grandparents provide clothing, additional support for child. Custodial parent has not signed form 8332 and child support is not consistent. Can the custodial parent let the grandparent claim children.