We all know that Oda likes using Myths, Legends and Fables (fable backwards = Elbaf btw) and converting them, and as i was reading some old chinese myths when somthing hit me.
There are said to be 4 seas in chinese mythology North, South, East and West....(hmmm that sounds familure)
They in turn are represented by four colors Yellow, Blue, White and Red....(hmmmm those colors are familure too..)
They have also been represented by different animals over time including a Monkey, a Bird, a Dragon, and a Dog....(that was when something pinged)
A north sea with a yellow monkey =Admiral Kizaru??
A south sea with a blue bird = Admiral Aokiji??
A west sea with a red dog = Admiral Akainu??
Which just leaves the East sea with a white dragon
This is all speculation but it would explaine why Dragon is the most wanted man alive. After all if one of the World Goverments top people defected and turned against them they would probably want him dead no matter what...
Also considering how much Garp was trying to train Luffy into becoming a Marine its a safe bet to say he did the same with his own son.