Nick Carter gets a restraining order against Aaron, claiming that he had threatened to kill his wife

Nick Carter said his brother, Aaron, did not leave him any other choice than to seek legal protection after declaring that Aaron had threatened to kill Nick's pregnant wife and unborn child … although Aaron had said that he would never hurt his family.

According to the Temporary Restriction Order obtained by TMZ … Aaron must remain at least 20 meters away from Nick, his wife, his children and other family members, including their residence in Las Vegas.

Nick said that he and his sister had been forced to ask for orders against Aaron. "Given Aaron's increasingly alarming behavior and recent confessions, he has thoughts and intentions about the murder of my pregnant wife and my unborn child."

A representative of Aaron told us: "I am stunned by the charges against me and I do not wish to harm anyone, especially my family."

Aaron seemed to make fun of Nick on social networks, saying that he should send a letter of cessation and abandonment while he was there. Aaron adds that he has not seen Nick for 4 years and that they are not planning a meeting.

As we have reported … The family of Aaron has been extremely concerned about his mental state lately, and the singer has expressed concerns about his mental stability.

Nick says, "We love our brother and really hope that he will get the proper treatment he needs before any harm comes to himself or anyone else."

Aaron appeared on "The Doctors" and at least a spectaclehe seemed to be suffering from anxiety, schizophrenia, multiple personality disorders and manic depression – another term for bipolar.

Members of the A.A County Sheriff recently went to Aaron's home in Lancaster, California, for a welfare check … and he claims that they visited him during the weekend and tried to place him in a psychiatric position of 5150.

Aaron flaunts his collection of firearms – He says that he owns a 9mm handgun, 2 assault rifles and other guns – and we learned that the cops are studying a obscure law it could be used to take up arms.

Aaron arrived on Tuesday on "TMZ Live" to challenge the idea that he was struggling with his sanity and telling his family to leave him alone.

Clearly, the feeling is reciprocal.