Question: Were Queen Esther’s children raised as Jews?
Answer: You are asking an excellent question. I can’t give you a definitive answer, but I can give you food for thought. In order to serve G-d as a Jewess, without being turned in and stopped, Esther acted in ways that were hidden. The very name Esther means, “concealer,” and she was able to conceal from King Achashverus her Jewish origins. Esther had seven chambermaids and assigned each one to attend her on a different day. This way the maids of the first six days would not notice her very different behavior as she observed her Jewish requirements concerning Shabbos on the seventh day, and the maid of the seventh day would simply think this was how Esther lived every day.
As Judaism passes through the mother, her only child Darius was Jewish, as you know. I do not know what measures Esther took with regard to protecting Darius as a Jew, but we can see one of the results that does make one wonder. The Second Beis HaMikdash (Holy Temple in Yerushalayim) was being constructed, when the virulently Jew hating Vashti, was instrumental in having her husband, Achashverus, halt the construction. Know that Vashti was the granddaughter of Nevuchadnezzar, the king responsible for the destruction of the First Beis HaMikdash. The only child conceived by Esther through Achashverus, Darius, after ascending to the Persian throne, allowed the construction on the Second Beis HaMikdash to be continued through completion
Regards, Eliahu Levenson