I have heard of Lupus occuring in more than one family member like an aunt and a niece. However, there a many people that are diagnosed with Lupus and have no other family member that has it. In my case, I don't have any family members with Lupus.
Also, if one family member has an autoimmune disease, it is not unheard of for another family member to develop another type of autoimmune disease. I hope this helps.
It isnt directly hereditary as in if your mom or dad has it you will. It is more like you are more susceptible to an auto immune disease if you have other members of your family with them. My sister and I both have Lupus but prior to that the only autoimmune disease that is in our family history that we know if is Rheumatoid Arthritis which my grand father had. We are both 1/4 Cherokee and I have read that there is a predominance of it in American Indians.
It also takes a trigger though. In my case my dr believes it was my metal prosthetic jaw joints and meningitis. In my sister's case it was mono.