Unfortunately, not much is known about whether or not Lupus or other autuimmune diseases run in families. There are many theories, but no definitive proof. In my case, I have Lupus, Fibromyalgia, Raynaud's and Sjogren's and not one person on either side of my family has or had RA or Lupus or any other like condition. The doctors have no idea how I ended up being blessed, as it were.
As far as medications, I too have a life threatening allergy to sulfa and all of its derivatives, which we found out the hard way when I was 9 and they gave me sulfa for a bladder infection. I am currently taking several medications, none of which conflict with my allergy.
Good luck and let us know how it goes.
"If you think you can, you can. If you think you can't, you're right". - Mary Kay Ash