Who was Esther's "father's house"?

Question

Esther is warned when she resists visiting Achashverosh that, if she demures, salvation would come from another source and וְאַ֥תְּ וּבֵית־אָבִ֖יךְ תֹּאבֵ֑דוּ "you and your father's house will perish."

But Esther's parents were dead and there is no mention of siblings (especially as her mother died in childbirth according to one version I heard).

Some meforshim tie this to the memory of Sha'ul; if his descendant (Esther) doesn't make up for his allowing Agag to live, she and her father's house will be lost through Sha'uls' sin -- from the Megillat Setarim via Sefaria:

והטעם היות כי המן נצמח ע"י חטא שאול באגג אשר הניחו חי ומזה יצא המן והוצרך שתהי' הצלה ע"י אסתר שהיא מזרע שאול ולזה אמר מרדכי שבאם ההצלה יעמוד ליהודים ממקום אחר ממילא היא ובית אבה יאבדו בחטא שאול שלא יתכפר לו (אלשיך):

but that still doesn't explain what her father's house IS and who it includes and how it would be lost. If the meaning is that SHE will die and thus not have children, would we associate her child with her father's house and not her husband's family's "house"?

Answer 1

R' Moshe Yitzchak Ashkenazi in Ho'il Moshe on the Megillot writes that Mordechai is referring to himself; that he will perish with Esther:

"ובית אביך. גם אני אבד עמך."

And so writes Rabbi Yosef Nachmias:

"ואת ובית אביך...שבית אביה האמור כאן רמז למרדכי..."

R' David Halevi in Divrei David writes (also here) that if she doesn't act upon Mordechai's message, it will be a disgrace to the memory of her parents:

"...אלא היינו מפרשים דבית היינו אנשי הבית כמו ואת ובית אביך תאבדו, והכוונה שלאנשי בית אביה יש גנאי דאמרינן בעלמא רשע גנאי לו ולמשפחתו...ויש מוסר בזה דהאב והאם חייבים בזה הזנות שבביתם היה הזנות ולא נזהרו לשמור אותה כראוי..."

Translation: "...but we shall explain that "house" meaning the people of the house, like "you and your father's house shall perish". and it means that the people of her father's house are disgraced as we say an evil man- it is a disgrace to him and his family...and there's a moral here for the father and mother are guilty of this immorality that is in their house, there was this immorality and they were not careful to guard her as needed..."

In a drashic fashion, Rabbi Shalom Shechna of Pohrebysche explains that "makom acher (a different place)" means receiving assistance from the Sitra Achra and "at (you)" means the Written Torah and "Beit Avich (your father's house)" means the Oral Torah. Mordechai's fear was that if the Jews aren't saved while remaining faithful to the Torah, they would leave it and simultaneously request assistance from dark forces.