Man u just raised my questions even more.
Lets see Acno has been round for 400 years or so. If Ierene was the former queen of dragons, how come acno doesn't recognise or know about her. Though Ierene seemed to know who he was the moment she saw acno in his human form.
Secondly if Ierene truly was the queen of dragons, then maybe she was before Acno, which would make her like 400++ years old!! Which is very unlikely, bit possible. Also there is another fact thats playing in my mind - Rather then being supreme Queen of dragons, she maybe a dragon queen of an certain element. Like - Igneel (King of flames) / God Serena used a ds water attak of the sea dragon king, something like that.
For now its way to complicated to jump the guns.