An evil, despotic ruler orders all persons of your Race, birthplace, and approximate age put to death. As far as you know, you are the only one to escape this heinous act. (work with your DM to determine details)
Rivalry: A rival to you or your family cause upheaval forcing you to relocate possibly to a far distant land. (Work with your DM to detirmine the details)
In adulthood you have an encounter with an unusual person, who as far as you can tell, has no home or family. You offer to help in anyway you can. After accepting your hospitality the stranger vanishes leaving a note "Your kindness will be remembered".
Political. A politcial enemy might inlcude a local magistrate, a noble who rules the region, or a monarch ruling the kingdom. the NPC might have offended a local ruler,become an outlaw, or a be a political rival.