User blog comment:12th Supernova/Chapter 743 discussion/@comment-1595565-20140403164819/@comment-10543621-20140404063147

I don't think the 'older master' necessarily has to be around for Doffy to be addressed as young master. This is the case for Chinese at least (and I'm pretty sure it's the same for Japanese), but there's actually no translatable term for master alone. It's either young master or old master, which usually refers the Dad or the son. Servants address the head of the houshold or the father as old master, and the son as young master. I'm pretty sure there's no way to translate master alone without the old or young.

So in agreement with others before me, the easiest explanation as to why they call Doffy young master would probably be because they Doffy's dad as well. Perhaps they were servants in the Celetial dragon household that held more loyalty to Doffy (which is not uncommon when servants spend their lives taking care of the child), and followed him when Doffy decided to start a pirate crew. Something along those line I'd say.

I personally don't think Doffy is on happy terms with his celetial dragon family. He must have enough ties with them to get what he wants, but I'm seeing him more as the wayward runaway noble son (kinda like Sabo???). Otherwise, I wouldn't be able to understand how a typical celetial dragon would allow their son to be a pirate. Unless by their twisted logic, since they own the world, they can do whatever they want, and so his parents love him so much that they agree with whatever he wants, OR Doffy's parents are very different sorts of celetial dragons from the typical ones we've seen, and are perhaps indicative that not all the celetial dragons are useless oafs, and perhaps some of them actually are sick and twisted in other ways.