If you want to be real and dramatic, you may follow the next general steps:
- Play with two characters. First was forced to join the nationals as they took his town. Second, living in a near town was forced to join the reds.
- Play some missions with first character, other ones with the other.
- Near the end of your campaign, eventually, both got involved in a battle (choose which character to use here as player). In this mission the other character was captured by the player's team. The player recognized the other as his real brother minutes before he was executed.