Is zakat obligatory on the money in my relative's possession from the loan we shared?

If one of the partners repays the entire joint loan, he becomes a creditor to the other, and zakat on this debt becomes obligatory for him.

The details are as follows: If the debtor acknowledges the debt and is capable of repayment, then zakat on the debt is due for him every time a year passes. However, if the debtor is insolvent or denies the debt, zakat is not obligatory until the debt is collected, and it is zakat for one year only.

It is permissible to borrow from a bank if it is a qard hasan (interest-free loan). However, a loan with interest is usury (riba), which is prohibited.