This link contains all pertinent information regarding the Service Star Banner, aka The Blue Star Banner. There is one star on each banner for every immediate family member serving in the Armed Forces during a time of war. If you see a gold star instead of a blue, then a serving family member was killed or died while in a time of war. Ask your parents or grandparents about it. They'll most likely remember it.

Service Star Banner - How to recognize military service in a family