I am not sure what your specific question is so I will offer general advice. What you know about this situation is that he is estranged from most of his family. They do not allow him to be in the presence of the family. One family member had a restraining order placed on him. What you also know is that he told you he has a serious mental illness but isn’t sure which one. It may be bipolar disorder.
What you don’t know about him is why he has strained relationships with most of his family members. Why have they banned him from family events? What happened the day he was arrested at a family event? What type of “scene” did he cause? Why was there a restraining order placed on him by his sister? Before you pursue a serious relationship with him you need to find the answers to these questions.
It may be that he has a serious mental illness and his family has “given up” on him. What I mean is that sometimes families can become frustrated with a mentally ill family member and decide (usually for their own mental health stability or well-being) that he or she brings the family too much stress and they have to cut ties. I have worked with families for instance in which a mentally ill family member refuses to take their medication and abuses drugs and alcohol. By using the illegal substances and not taking the medications, the ill family member might become angry, out-of-control, violent and difficult to handle. If this situation were to occur repeatedly the family might grow frustrated and attempt to exclude the family member completely from their lives.
It might also be that his family simply abandoned him. Sometimes families stop interacting with their ill family member because they may fear that the ill member might tarnish their standing in the community or make them look bad.
I can only speculate as to why his family refuses contact with him. It’s important to find out why.
You said that he was hospitalized for two weeks after his arrest. Do you know what the grounds for this hospitalization were? Was he committed or did he go willingly to the hospital? It would be informative to know why exactly he was in the hospital.
The bottom line is that you need more information about him before you pursue this relationship. You said that you will see him in person in three months. Three months might be an adequate amount of time to learn more about him. Through interacting with him you’ll start to learn more about his personality and hopefully more about his personal and family life.
You should also try to gain information about him such as why did his sister have a restraining order placed on him. Was it because she was overreacting or was it because he tried to harm her and she feared for her safety? Why was he hospitalized? Why was he arrested at the family outing? Was it because his family exaggerated his behavior because they could find no other way to get him to leave the day of the family function or was it because he was a danger to himself or others? Has he been arrested before? Does he use drugs or alcohol? Why does he think he has bipolar disorder? Is he being treated for this disorder? Has he ever had another diagnosis? As you said he was at the hospital for two weeks but claimed that he was never diagnosed. Usually with every hospital admission a diagnosis is given. Did he just not agree with their diagnosis? You need to know all of this and much more before you pursue this relationship. Ask many questions and know who you are dating. That’s my general recommendation. Thanks for writing.