User blog comment:Zeref Fullbuster/Dabi is Shoto's eldest brother Toya/@comment-43973617-20191001065317

You guys look at Dabis burns, They're in the exact same place as Endeavors flames. I think that Endeavor treated Dabi the same way he treated Shoto, but when Endeavor thought Dabi could do the same thing as him but something went wrong causing him to get burned extremly bad, and after that he despised superheros and became a villian. But thats just a theory.