Each Interupt has a fixed Handler Address.
If they have the same priority, the second will run after the RETI of the first.
A higher priority Interupt will interupt a lower priority one.
A lower priority will run after the RETI of the first.

In "C" be care full with the registor bank choices. They will affect RAM usage and Interupt overhead.

Note that you can poll to see if the inerupt happens in the other one, but that defeats the purpose.
I am assuming your Interupts are as short as posible.