A vicious animal attacks you on a moonlit night. Friends drive the beast off, but you discover that you've been cursed with lycanthropy, to become a similar beast under the full moon. (work with your DM to determine details)
During your early adulthood you saved someone's life. This person becomes your companion. (work with your DM to determine details) Roll 1d10 on a 9-10 your companion falls in love with you.