Declare war to an Overlod while HE is at war

[Deldras]

picture this: there are 2 empires vassal of the same overlord, they grow closer and happy together and then decide to challenge the master empire and break free.
One of them declare war to the overlord, the other one wants to help but... he is in war with his friend.
So how can 2 vassals coalize to defeate the common enemy?

 

[Chilled Legumes]

I would assume you can invite them to the war, can you not? I've never played as a vassal myself, so I'm not 100% but i'd assume that's how it should work. Also, would declaring a war of independence from your overlord not remove you from their own wars?

 

[Deldras]

My friend said he couldn't but he's not the best with english and real time understanding so I may have to check it myself.