John
It would never be a debt, as I would never ask anything in return.
However, I'll indulge you. When I knew you before, you'd done something extremely reckless and died. At the time, I was with your son Sam in a very romantic sense and your death destroyed him. I traded my godhood for your life. When I died giving birth to Sam's son, the Fates returned my godhood. The death of one of upsets the balance, you see. But during our wedding ceremony, I vowed to love Sam forever, and I have. Protecting you and yours comes as part of that love.
You must understand, he knows nothing except he and I were married once.