Not sure whether you mean time for the medical aspect or for the bonding aspect. You should consider those separately.
Medical: yes, your pay policy should be one for any type of medical leave (which would include pregnancy). You shouldn't pay maternity leave and not pay for a man who broke his leg to also be out for the same period of time.
Bonding: You would not be required to pay for a dad who wanted to take off bonding time to be with his child, just as you would not be required to pay for the portion of maternity leave for the mom that is bonding time (Regardless of whether you pay the medical time). But if you pay for mom though to bond, you better be prepared to pay for dad to do so also. Otherwise, yes, you could face a discrimination due to gender charge.
That said, you also need to check state laws. I know some states, like CA, have some really weird interactions between medical leave and paid family leave.