Zend certified PHP/Magento developer

Can I have a modem/router going to 2 computers then also have another router going to 2 other computers with all getting internet

I have a modem/router in one, and it’s going to 2 computers itself. Then I have an Ethernet cable going to an unmanaged switch, then from the switch going to 2 different computers. All have Ethernet connection.

I have a PfSense router as my 2nd router and one of the 2nd computers are that router.

Can I have internet going thought both routers and have my main computer which is the other computer on my switch going through my PfSense? So modem/router to 2 computers getting internet from that. Then from that modem/router to an unmanaged switch to PfSense to my main computer.

I only want my Main computer going through my PfSense. Is this possible? Can I only have 1 computer going through PfSense, or does everything have to go through it?

I don’t want to set up PfSense to everything because it’s in one room with my main computer, nothing else is in here.