User blog comment:DancePowderer/Where There's Vinsmoke, There's Power Part 2/@comment-5623290-20160202214746

I always thought that his family was on a cruise ship of some sort that got shipwrecked, and somehow Zeff saved him, but got stranded on an island/rock. And due to Zeff sacrificing so much (his leg) as well as starving together, Sanji learned to appreciate food and Zeff's craft, leading to his life goal and dream.