Question ?

In this picture you can see my current situation. I only need one province from Haixi to form Manshuria but they are allied to Oirat and Orochon. I am Also allied to Oirat but Haixi and Orochon are my rivals. I do not have any dlc because im still new to this game. What can I do in this Situation

Ps: couldnt upload a screenshot. Sorry