I have been executor for several people after their passing. et me tell you it is a bitch of a job. The heirs are usually impatient assholes. Nobody understands the legal hurdles, regulations, and timing. If the estate is anything and the will is not all specific bequests, there is a lot of time needed to get it done.
Also I have never heard of a "co-executor." I can only imagine that would cause 100 times the problems by not having a single authority. Sooooooooo that part of the fable Ima gonna throw out the bullshit flag on.