Brother Refuses To Sign Probate Document

Location: New Jersey. My mother-in-law’s (60sF, lives in Florida) parents died in spring of 2025. Since then she has been the executor of their estate and going through the process with the probate lawyer. She has one living sibling, her brother (60sM) who lives in New Jersey (same state that the parents died). He has been incredibly emotionally abusive to MIL throughout the process (e.g. daily texts and emails abusing her, menacing her by sending her pics from Google earth of her house, veiled threats that he will hurt her).

Now that probate has wrapped up, the last step is that the brother needs to sign a notarized form stating that MIL fulfilled all responsibilities as executor and that he has no concerns/disputes about her performance as executor. The brother is refusing to sign. He has stated many times via text/email that he doesn’t have any concerns with her performance as executor and that his reason for not signing is (A) MIL is taking the percentage of payment for being executor that is legal under NJ law, and (B) their issues in the past unrelated to probate.

The probate attorney told MIL that she will need to take the brother to court but the probate attorney is refusing to represent her in that process (he says he’s too old for this and doesn’t want to deal with the brother’s BS anymore).

What are my MIL’s options?

Note that the estate in question is under New Jersey jurisdiction. MIL’s physical location is in Florida.