Yes.
Your father who cosigned student loans may claim the student loan interest deduction on his portion that was paid. To claim the student loan interest deduction, the borrower must be legally obligated to make the payments on the student loans and the Student must be a dependent of the Cosigner. Cosigning the loans counts as legally obligated to make the payments.
You can also deduct the portion you paid.
Please see FAQ (below) for reference. https://ttlc.intuit.com/replies/3302319
