Whilst people are free to do whatever they like I have to say I wouldn't acknowledge someone who claimed to be related directly to the Allagan Empire. Maybe if it was done exceptionally well but in my experience most of the people who drift towards that sort of thing end up pulling it off poorly and come off as a special snowflake.
It doesn't strike me as very plausible given that we're explicitly shown in-game that individuals with Allagan blood are exceptionally rare. It's the sort of trait that forces people to acknowledge someone's character as being on the same level as major lore characters - and as far as I'm concerned there's plenty of ways to make a character's backstory intriguing without doing stuff like that.
It doesn't strike me as very plausible given that we're explicitly shown in-game that individuals with Allagan blood are exceptionally rare. It's the sort of trait that forces people to acknowledge someone's character as being on the same level as major lore characters - and as far as I'm concerned there's plenty of ways to make a character's backstory intriguing without doing stuff like that.