How do you know if a family member has borderline personality disorder?

How do you know if a family member has borderline personality disorder?
Signs and Symptoms

Intense fear of rejection, separation, or abandonment.
Rapid changes between thinking someone is perfect to believing they are evil.
Risky behaviors including unsafe sex, gambling, drug use, or accumulating credit card debt.
Threats of suicide or self-harm.
Difficulty empathizing with other people.

Signs and Symptoms
  1. Intense fear of rejection, separation, or abandonment.
  2. Rapid changes between thinking someone is perfect to believing they are evil.
  3. Risky behaviors including unsafe sex, gambling, drug use, or accumulating credit card debt.
  4. Threats of suicide or self-harm.
  5. Difficulty empathizing with other people.