Can't connect to Apex Legends server while on the same network

A disclaimer, I know that there is already a thread going on that addresses the same issue, but so far none of the solutions there has worked for me.

Hello, 

I am not able to play with my brother while we are in a party together. If my brother invites me to a party, I will be able to connect to the game, but my brother gets timed out. If I invite my brother to the party, the opposite happens. We had similar issues on R6 Siege, but it was fixed when I used a wifi adapter while he was connected to the router via ethernet cable. I have tried this "fix" for Apex Legends, to no avail.

Various other solutions we tried:

1. Turning off UPNP on the router, and turning off SSDP discovery and UPNP Device Host on both PCs.

2. Tried to port forward, but I have read that it won't work since I have to forward the ports on both PCs, which is not possible since we have 1 public IP address (not sure how to confirm this). 

There were some other potential solutions that seemed ridiculous to try. One apparent "fix" was to put one of the computers on DMZ. This is extremely dangerous as it exposes that PC to an array of viruses from the internet. They have also suggested using a VPN, but I am not going to subscribe to a VPN provider just to get this game to work.

I am not sure what is causing this problem, and I have went through archives of similar problems on other games like Diablo 3 and R6. This issue needs to be addressed by the developers, how can a game that emphasises team work not allow two people on the same network to join a server? Seems silly to me how other games like Overwatch, CS:GO, Dota 2 and even Fortnite does not have this problem at all, and yet a game that was released on 2019 still has a problem that were present in games published years ago.

Thank you before hand if any solutions are provided in this thread, and I'm sorry if some of the things I said are incorrect. Please point out the mistakes and I will address them. This game has so much potential and I would love to play it with my brother. Please, the developers have to address this.