No agreement signed

My brother and his wife are in the midst of a very ugly separation and eventual divorce. She drafted a separation agreement, which my brother did not agree with, and he filed a counter offer. She has not agreed to that, and instead moved out of their house, which she is still legally partially responsible for and has not paid the mortgage on. After moving out, she took money and all of their belongings, including items that were my brother’s before they were married. No separation agreement or equitable distribution has been signed, and I was wondering what this means for my brother. Can he take her to court and demand everything back? Will the court decide what she has to return, and will it be at her expense? In addition, she has yet to remove herself from her and my brother’s insurance policy, and according to their insurance statements, she is still listed as living at their house. Isn’t this insurance fraud?? I would appreciate any advice that I might be able to pass along to my brother.