Civil Strife! Conflict broke out during your youth causing social upheaval, your family was involved in the conflict (Work with your DM to detirmine your families involvement)
The home town where the character lives is destroyed, there is little loss of life. However, after the disaster passes, the area is rebuilt and becomes more prosperous than ever before. (work with your DM to determine details)
When you become an adult you learn to used a weapon (of your choice) appropriate for your culture and social standing. (work with your DM to determine details)