Nerina Irontail, Khamira Shadowalker, Camillia Burnbright are 3 Charr sisters who live in the Black Citadel, each one came from a different father but from the same mother, so each one went to one of the 3 legions.
Nerina the warrior and oldest and biggest went to Iron legion
Khamira the thief and smaller went to ash legion
Camillia the engineer and younger sister, went to the Iron Legion 
There is a rivalry between the sisters, since Ash, Iron and Blood Legion have different doctrines