Here's the deal, it's not a lineage of the Hokages, it's a lineage chart of WHO TAUGHT WHO. Yes, it's fanart, but what they're tryint to point out is, in terms of lines of teachers:

First and Second -> Third -> Jiraiya -> Fourth -> Kakashi
+ Jiraiya ->Naruto

The First and Second taught the Third, the Third taught Jiraiya, who taught the Fourth, who taught Kakashi, who taught Naruto. Any parallels on the relationship between Naruto and the Fourth is still under heavy debate.