Tanya, lupus is an auto-immune disease. There can be more than one member of a family with an auto-immune problem - not necessarily the same one, though.

For example, my daughter-in-law has MS and her father has Crohns. There are many, many others - like Type 1 Diabetes, Rheumatoid Arthritis and Grave's disease. And some poor people end up with 2 all by themselves