Sobekneferu’s much younger sister, Katherine’s aunt. Iset (or Isis) is almost 30 years younger than her sister, a very much loved ‘accident’ and only the 2nd daughter to their mother, Tetisheri, the previous Tigrin queen.
Influential Tigrin nobility have pressed for her to be declared Heir Apparent for over a decade, but Sobekneferu always resisted.
It is unclear what her role was in the last 14 cycles (~18 years), but now that the princess (Katherine) is back, she’s just another of the queen’s siblings, unless something were to happen to Katherine.