What are the chances of contracting strep throat even after testing negative previously?

Hello doctor,

I just wanted to inquire about the likelihood of contracting strep throat. Last week, my daughter was diagnosed with strep. Further, my father-in-law received the same diagnosis. My wife and I visited our doctor due to ear infections, and although we tested negative for strep, we were prescribed a Z-pack. Now, this week my brother-in-law has been diagnosed with strep. I am wondering if there is still a possibility that my wife and I could get strep even though we were taking the Z-pack. I do not want to tempt fate, but we took care of the baby all last week, and I tested negative twice while my wife also had a negative test. Are we in the clear, or is there still a chance of contracting it? My brother-in-law's doctor seems to believe that since the rest of the household uses antibiotics, we should all be okay. Please help.