Born as the youngest sister, after her older brother pretty much making her ineligible for being the newest leader. She is infertile and isn't able to make a family of her own, however since the twin's mother died, she's been taking care of her ever since. Her brother has been wrapped up in work for so long, his children rarely ever see him, making her basically the twin's only parental figure. She offered to train her niece once the decision was made to take her to Sunagakure, though she is a bit rough with her work. The training has only recently came to a end and she is just planning to stay in the village and watch over them, feeling like they both are her own children.
Agatha is a bit of a tradional woman, wearing stuff that nobles would wear and pretty much is the ideal form of manners. Though, when ticked she can easily lose her cool and can go berserk. Even though she isn't a shinobi, she has various skill in physical combat, making her one of the strongest clan members living. She doesn't like slacking and that has made Serendine's training really hard on her.
Refer to the image.