Due to my research, this can't be done.I don't think so. He can set them up for PC1 and PC2 separately if his router has that option.
Port forwarding for PC1
Port forwarding for PC2
PC1 and PC2 can be accessed at the same time.
A lot of gamers use that setup. Is there something wrong?
There isn't an option to open the same port for different IP addresses.
BTW, the DMZ server for PC1 and port forwarding for PC2 doesn't work either .