In need of Garlean Lore

[Balipu]

It's also possible that the "few few garlean that can use magic" might be a "pure blood" that doesn't know that somewhere in his blood line, there was a non-pure blood children (adultery somewhere ?)
But in this case, if the child doesn't have the third eye, it would be impossible to hide so it's just an hypothesis.

Yeah but how pure is pure? We know Eula Darnus had some Allagan blood, but she had the third eye. Although her magic came from Bahamut.