If your parents, filing together, have a $0 tax liability for the year - and they are only filing to claim a refund of taxes withheld, then theoretically you could claim your Mom. But if one of your parents earns enough income to require them to pay taxes, then neither of them can be claimed as a dependent by someone else.
Does your parents combined have enough income that they have to pay some taxes? (Not that they owe at the end or the year - but they do not get back all of the taxes that were withheld).
