Deductions & credits

To deduct property taxes, you must be a legal owner of the property, and you must be the person who actually pays the taxes.  

There is nothing in particular that says you must pay the city or county directly yourself, it would be acceptable for you to reimburse the other owner if they paid the tax at first.  But if audited, you would have to prove it.  It would be easier to prove if you directly paid the city or county.