<p>According to Ghazan's wikia page (
http://avatar.wikia.com/wiki/Ghazan), the moustache came into existence at 10 years old. In which case either Ghazan being raised by a sister or the unspoken attraction is true.
</p><p>I'm thinking that the unspoken attraction is likely, given that since it's the four of them together most of the time (excluding their imprisonment) and that Zaheer and P'Li are already an item, it could be the case that Ghazan and Ming-Hua would be attracted to the only single person in the group that they see most of the time (ie each other). Not to mention the two of them were like partners in crime as they'd be fighting together in 2v2s (Mako and Bolin vs Ghazan and Ming-Hua (one of which was on P'Li's orders, I know), all confrontations (As well as the brief confrontation of Mako, Bolin and Asami vs Ghazan and Ming-Hua), and Kya and Bumi vs Ghazan and Ming-Hua.
</p><p>Initially I thought that any non-business related talk (ie kill the world leaders, kill the Avatar, change the world etc) was more sarcasm and small jokes between the group (all but Zaheer who was always pretty serious about the group's goals) such as Ming-Hua being happy to see the two mug-heads, or P'Li calling Ming-Hua out for being a show off for not using the elevator. Even so, I think that some sort of romance between the only people they'd regularly see whilst out on their business trips is likely, since there was never really anything else to suggest that Ghazan had an older sibling.
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