Okay just finished the Human Division from the Old Man War series and really just got to know. Will we every find out who is stealing the Conclaves and Unions ships? Then are these the same people who kidnapped the Unions soldiers and destroyed earth station and been attacking the Conclaves and Union ships?
Yes, in the final book The End of All Things we find out who is stealing all the ships and why. Yes, it is the same group responsible for all the various things.
In End of All Things we learn a group called Equilibrium has been formed with goals which including destroying the Conclave and Colonial Union. It does this by capturing ships and crews, and using CDF style technology to connect a brainwash pilot's brain directly to the ship's computer. These captured ships are then generally sent on suicide missions.
Equilibrium includes members of many species, including some CDF and Conclave traitors.