Hello and thanks for using Just Answer.
My name is ***** ***** am happy to assist you with your enquiry.
Please be rest assured that the step brother has no power whatsoever to change his Mother's Will.
An Attorney only has power to look after the party's affairs, and should keep accounts of monies being spent ontheir behalf. Their powers do not extend to doing anything with the party's Will.
I hope this clarifies the position to you.
Thank you very much.