According to the game rules and Alex's own words, sharing a network is not itself against the rules. However, there are some restrictions that apply between those nations that cannot be evaded, but I think some (if not all?) are lifted if you choose to get verified.
Feel free to read here: https://politicsandwar.com/rules/
You can also find out about verification here: https://politicsandwar.com/account/verification/
Hope this helps~