student loan interest

Do you have a legal obligation to pay that interest? That is, at the time the debt was incurred, did you agree to pay back the loans, and if so, under what conditions? If you are not legally obligated under the terms of the loan to make payments on the loan, you cannot deduct any interest you paid. Also, if you are only liable on the loan as a guarantor, and only obligated to pay if and when your child cannot pay (i.e., has defaulted on the loan), then you also cannot deduct the interest you paid. Even if you're not liable under the express terms of the loan, you should check to see whether you have any liability under state law for the debts of your child (if the child is 18 or over, you probably don't, however).

Also, what if I am the co-signer on the loans?

Co-signors of the loan are fully liable for payment, including interest.