Hi, sorry for taking to so long to get back to you.
I'm not sure if it works via VPN, since I have no experience with this.
What my friend and I always do is one of us launches steam, goes to offline mode and then runs Civ.
Then the other one launches steam, logs in with the same account, then changes the profile name and launches civ as well.
Then we can host and join the same LAN game.
If you can connect to a LAN game via VPN, this method should work just fine for you.
I'm not sure if it works via VPN, since I have no experience with this.
What my friend and I always do is one of us launches steam, goes to offline mode and then runs Civ.
Then the other one launches steam, logs in with the same account, then changes the profile name and launches civ as well.
Then we can host and join the same LAN game.
If you can connect to a LAN game via VPN, this method should work just fine for you.