Esther had not revealed her nationality and family background, because Mordecai had forbidden her to do so.
References for Esther 2:10
Every day he walked back and forth near the courtyard of the harem to find out how Esther was and what was happening to her.
Before a young woman’s turn came to go in to King Xerxes, she had to complete twelve months of beauty treatments prescribed for the women, six months with oil of myrrh and six with perfumes and cosmetics.
References for Esther 2:12
And this is how she would go to the king: Anything she wanted was given her to take with her from the harem to the king’s palace.
In the evening she would go there and in the morning return to another part of the harem to the care of Shaashgaz, the king’s eunuch who was in charge of the concubines. She would not return to the king unless he was pleased with her and summoned her by name.
References for Esther 2:14
When the turn came for Esther (the young woman Mordecai had adopted, the daughter of his uncle Abihail) to go to the king, she asked for nothing other than what Hegai, the king’s eunuch who was in charge of the harem, suggested. And Esther won the favor of everyone who saw her.
References for Esther 2:15
She was taken to King Xerxes in the royal residence in the tenth month, the month of Tebeth, in the seventh year of his reign.
Now the king was attracted to Esther more than to any of the other women, and she won his favor and approval more than any of the other virgins. So he set a royal crown on her head and made her queen instead of Vashti.
References for Esther 2:17
And the king gave a great banquet, Esther’s banquet, for all his nobles and officials. He proclaimed a holiday throughout the provinces and distributed gifts with royal liberality.
References for Esther 2:18
When the virgins were assembled a second time, Mordecai was sitting at the king’s gate.
References for Esther 2:19
But Esther had kept secret her family background and nationality just as Mordecai had told her to do, for she continued to follow Mordecai’s instructions as she had done when he was bringing her up.
References for Esther 2:20