"I am one of two siblings. I really hope I don’t have to go through any of this for a very long time but I really don’t have a clue how things are going to unravel because at the present we are both power of attorney and my brother continues to make all the decisions, not that that has been a huge issue so far. What I am worried about is when she passes, my mother has made us both executers of the will and I don’t communicate very well with my brother as he has always just done what he wants and thinks is best. What do you recommend and is there a system that regulates how things are dealt with?"
Normally I would suggest to someone who is reluctant to act as executor to make sure they tell that to the person who has named them. However, since you and your brother are acting under the POA, I assume that your mother is having some issues with capacity. This means she is likely not able to make a new will or codicil that removes you as an executor (or removes your brother, or whatever she would choose). There is no point distressing her by telling her that her plans won't work out, if she isn't able to change them.
So, given that you are prevented from doing anything pro-active about the situation, you will have to do something about it once your mother has passed away. Here are your options, as I see them:
1. Renounce (or give up) your right to act as executor and let your brother do the job alone. If you are considering this option, make sure you do this right at the very beginning, otherwise you lose the chance to renounce and will require court permission to quit. You said that your brother mostly does what he wants and thinks is best, and you don't seem to have a problem with his intentions or outcomes. Assuming you trust him to do an honest job of it, perhaps it would be worth giving up the job of executor to maintain a good relationship with your brother and avoid the struggles that may occur.
2. Take on the job as directed in your mother's will, knowing that it's going to take some real effort to communicate effectively. If you two act as co-executors, you will both have to sign documents and you'll have to agree on many things, from the selling price of the house to who is going to get the family photo albums. It might not be enjoyable, but it can be done.
3. If you two simply can't manage the estate together because of communication issues, consider hiring a trust company to manage things as agent for both of you.
I doubt that your mother even considered the question of how you two would manage together. Very, very rarely do parents think about that. They are usually more concerned with treating you both equally and not appearing to favour one child over the other.
You asked if there is a system that regulates how things are dealt with. There is nobody from the courts or the government who automatically oversees how estates are going. The only system that deals with estates is the court system, and only if someone goes to the court and starts a lawsuit. So in other words, an executor can run off in all directions, lose money, screw up the papers, upset everyone - but the courts won't know or become involved unless someone files a complaint. The "someone" I mention is usually a residuary beneficiary of the estate.
Most executors rely on the professionals they've hired, particularly the lawyer who applies for probate, to give them advice on what they need to do. This arrangement has its limitations, as the lawyer works for the executor, and not the other way around, so the lawyer can't force an executor to do anything.
I hope this gives you a better idea of what may be coming down the pipe for you.