There's a slight error in Sonya's profile; both Marla and Hestia are older than her. Marla is the oldest, Hestia is the middle one, and Sonya is the youngest.
The translation here says Marla is the youngest one, is this an error in the Japanese profile? (the original FE2 says Sonya is the youngest but doesn't specify which or Marla and Hestia are the middle/oldest; the ingame help descriptions for Marla and Hestia in SoV do though)
(Edited because I originally had the ages of Marla and Hestia switched hehe)