In the first generation of Fire Emblem: Genealogy of the Holy War Sophara is ruled by an unknown lord, who was the father to Chulainn. It is unknown what happened to that lord, or why Chulainn left Sophara and ended up in the Evans arena.
In the second generation, after the conquest of Isaach by the Grannvale Empire, it was ruled by Iucharba of Dozel. Due to the kind nature of Iucharba, Sophara did not follow through with the Empire's child hunts.
Sophara, along with the rest of Isaach is liberated by Seliph and his liberation army after Chapter 6, however, whether or not Seliph must seize Sophara is dependent on whether Larcei recruits Iucharba or his brother, Iuchar. If Larcei talks to Iucharba then Sophara will become an Other-ruled castle, however if she talks to Iuchar then Sophara will remain under enemy control, and must be seized.