Y/N and Aaron have known each other since they were babies. Their parents are close friends, and the two were born 1 month apart (Aaron on November 2 and Y/N on December 2). They have always been each others very bestfriend, even now in adulthood. Aaron chose a career in the BAU, and Y/N chose a career in nursing. Y/N joined the Army to be a combat nurse shortly after getting her nursing license, and has been on a tour for 10 years. She has been able to stay in contact with Aaron through letters back and forth, but they haven’t seen each in person. On Aaron’s birthday, Y/N is finally coming home from her tour. She shows up at the BAU to surprise him without having told him prior that her tour was finally over.