Breach of Confidentiality by a Private Investigator

[noir49]

My question involves an injury that occurred in the state of NJ

My brother has 2 kids with his ex girlfriend, who has a new boyfriend. The kids told their father some objectionable things about this man and he became concerned about them being with him. The ex gf denied these things and said the kids were exaggerating. So, he tried to hire a private investigator to check him out and also observe them together to see what was going on. No one would take the case because he wasn't actually dating her. So, he found a different p.i. and said he was dating her and thought she was cheating. He took the case and worked it for a while. Then, he somehow found out the story was bogus and my brother believes, he may have even hacked into his emails, etc. From things that transpired later, it seems like he also breached his confidentiality agreement. Even though this investigator was hired under somewhat false pretenses, he still violated his agreement. Can the investigator be sued? My brother also thinks it may be possible that the investigator may have actually been hired by his ex gf to get into his online accts and do surveillance on him. Since my bro and his ex live in different states that also means that by working for his ex and doing surveillance on my brother, he was working in a state in which he was not licensed.

[Mr. Knowitall]

Can the investigator be sued for what? A wild claijm that "it seems like" the investigator violated his confidentiality agreement? There would be nothing to stop you from filing such a lawsuit but without evidence you'll lose in short order. Also, what are the economic damages that would justify filing a lawsuit?