Hey man, sorry to hear that. My mom had Lupus. It can be a rough disease. The important thing to share with your brother is be patient with her, because it can be very frustrating. She may experience a lot of symptoms similar to arthritis, (reynoids syndrome) and some mood changes. For people suffering with Lupus, it can be very difficult because it is not a well known disease. Also try to keep her stress free. Lupus feeds on stress. Often during a lupus flair up, the body's immune system will begin to attack healthy organs. Sort of the opposite of HIV where there is no immune system, lupus brings about an over-active immune system.
Look I am no doctor, but I have experieced a lot with this disease and have some understanding.
Be Well.