I need a convincing background for two of my characters; a pair of twin brother/sister soldiers. Here is the concept for them so far: the twins serve in the same commando unit (I'm not sure if it's an existing unit, like the Green Berets or Delta Force, or if I should invent a fictitious one for the story). For the sake of this post, I'm assuming women have finally been allowed to serve in combat regiments alongside men. The brother is in a leadership position, and the sister is a technical genius/computer whiz. The problem lies in their background. As stated before: I'm not sure what commando team they should belong to, or if I should invent one for them, either as a new unit created before the story begins, a unit that exists only in my story with its own history and traditions, or a special, top secret unit. I'm also not sure about rank. Originally, the brother was a major, and the sister a captain. The sister reports to her brother. The two are 27 years old. Any ideas on how this arrangement could have come about (West Point graduates? My original explanation: recognition for past heroics as enlisted personnel? Something else?), or should I demote them a few ranks to make them more believable? And if it turns out none of this is plausible, then I could use some suggestions as to how to rework the two into paramilitary roles. Militias are out of the question: the twins are urban Japanese-American, and militias are primarily rural white Americans. Mercenaries, perhaps? Part of the plot calls for them to be familiar with a sergeant serving in the regular Army, and work with him and his company on the front lines of battle, or accompany him and his commanding lieutenant on errands in the rear. How could this work out if the twins are paramilitary, instead of military? I'd appreciate your responses.