Bosnia and Serbia, right? Your only option without cheating is to unvassalise them then conquer them like any other nation.
With cheats you can press ` to open up the console and type "annex SER" then hit enter. That takes care of Serbia, then do "annex BOS" for bosnia.
With cheats you can press ` to open up the console and type "annex SER" then hit enter. That takes care of Serbia, then do "annex BOS" for bosnia.