What term refers to the unique circumstances surrounding soldiers whose siblings have died, been captured, or are MIA?

The correct term that refers to the unique circumstances surrounding soldiers whose siblings have died, been captured, or are Missing in Action (MIA) is the Sole Surviving Son/Daughter designation. This designation is specifically designed to recognize and protect service members who are the last surviving child in a military family where siblings have faced extreme circumstances including death, capture, or being MIA during military service. The intent is to offer some consideration and support for the emotional and psychological challenges faced by these individuals.

This designation can impact various aspects of military service, including assignments and potential exemptions from certain duties, as it acknowledges the sensitive nature of their family situation and aims to ensure their well-being. It's important for soldiers in this category to have a supportive framework that acknowledges their unique circumstances, which is what the Sole Surviving Son/Daughter term encapsulates.