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)
Rebellion: As an adolescent you joined a rebellion against the local ruler, if successful you are outlawed, if it failed you escape, with only friends and family knowing your involvement. (Work with your DM to detirmine the details)
Approaching adulthood you experience wanderlust and decide to travel, roll 1d6 to detirmine years spent travelling and think about where your character might have gone. (work with your DM to determine details)