So i am currently playing as UFP. Roughly mid game. Have allot of vassals and subjects ect.

I am bordering Kzinti (whom i have no affiliation with, no defensive alliance, no subjugation not even a non aggressive pact), and they have decided to declare war on the Romulans.

Thats fine, however i can vote on whether they go to war with the Romulans? Why am i being asked when i am not in a federation with them?
I voted no, so i wouldnt be forced into a war with the Romulans. But why was i even involved?

I thought perhaps it might have something to do with my diplomatic weight? Or perhaps because i have a neutral zone with the Romulans?

Any help would be appreciated. :)