You could only claim the interest paid if you are on the loan.
"
if you are the primary borrower, you are legally obligated to pay the debt and you actually make the payments. If you are married and both you and your spouse sign for the loan, then both of you are primary borrowers. If you pay your son's or daughter's mortgage to help them out, however, you cannot deduct the interest unless you co-signed the loan."
https://turbotax.intuit.com/tax-tips/home-ownership/deducting-mortgage-interest-faqs/L4a9KF9mI
