A little under a year ago, I filed my first provisional patent (in the USA) with a very small group of people. Recently, it came to my attention that one of the co-inventors has added a bunch of other people as co-inventors to the patent. I find it very strange that (i) I was not consulted about this, and (ii) on the topic of these matters I was not cc'ed on any of the email to/from the patent law firm that is handling the patent application for us.
My question is twofold: firstly, is it legal? I.e., does any co-inventor have the power to add other co-inventors without the consent of other people listed on the patent? Secondly, is this acceptable behavior? Personally, I find it very strange and I feel a bit upset, but I am also very new to patents, so I might have the wrong expectations for how this usually works. Since it is still in the provisional stage, I could probably object and try to counter this move, but I first wanted to get a better sense of whether what they did is strange or not.