Invite to federation fails, other members vote no. How to force a yes?

[Conan]

The two empires are far away from eachother but both right next to my border, I can form a federation with one of them but when Inviting the other (or they ask to join) the other member always votes no. I tried buying up a bunch of favors and using them but it does no good. Is it just not possible?

[Doctor Proteus]

I don't think you can force them to vote how you want. If you can take full control of the federation by becoming the strongest and centralising all power, you can be the one to make all the decisions.

Or you could use the "yesmen" console command.

[The Grand Mugwump]

Raise your federation level and set it to president decides while making sure you're always the president. You can also use majority vote and diplomatic weight if you're big enough. However, if you're trying to force people who dislike each other into a federation, be prepared to shoot down a lot of kick votes and some members even outright leaving the federation. This is why the diplomatic weight vote is important too.