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)
Hostile encounter. Followers of a god are persecuting unbelievers, you had a direct or indirect interaction with them. (work with your DM to determine details)
You are magically transported to your current location, a land far away from where you were born. Any family or friends are left far behind, This event makes you a foreigner in the land in which he now dwells. (work with your DM to determine details)