The Talmud (Megillah 13a) says Esther never had parents – her father died when Esther was conceived, and her mother died when she was born. Mordechai took her for a daughter because her parents died. According to the Talmud, the word “l’bas” (“as a daughter”) can also he read “l’bayis” (“as a house”).1 A house represents a wife because a woman is the foundation of the house (Tehillim 113:9), meaning that Mordechai married Esther. Noda B’Yehudah notes that the verse’s use of the term “lak’cha” (“acquired”), similar to the Mishnah’s (Kiddushin 1:1) idea of Jewish marriage being, among other things, a legal acquisition. If they were married, why is the Megillah not explicit about this marriage? First, Rabbi Mendel Weinbach points out, one must realize that this text existed during Achashverosh’s reign, and his wife’s being married to another man would not bode well for her. Also, according to the Sfas Emes, this marriage was not explicitly stated because this verse also discusses her beauty. We should not think that Mordechai married Esther for those sorts of superficial reasons, but because he truly cared for her.
Finally, Ibn Ezra says that Mordechai only wanted to marry Esther, but did not actually go through with it. Similarly, the Maharal considers Esther a “bas zug” (“exact match”) for Mordechai, or perhaps a sort of character foil, as a wife should be a match for her husband (see Talmud, Shabbos 118b).
The Midrash (Esther Rabbah 6:1) tells us, that the verse in Tehillim which says, “Praiseworthy are those who keep the law, who perform kindness at all times” (Tehillim 106:3) refers to Mordechai because he adopts an orphan, and raising somebody is a full-time 24/7 occupation with kindness. Since many people in history adopted children, the Dubno Maggid explains that the Midrash connects this verse specifically to Mordechai because he also “keeps the law.” This great kindness was that first he followed the law, and then he did “chesed” (“kindness”). Many people do chesed, but without Torah, it is not real kindness, but token fluff. Rabbi Elisha Gallico reminds us of how great is the mitzvah of adoption. If Mordechai’s taking care of his niece earned him the honor to rescue the Jewish people, how much more so a person who adopts somebody with no relation to them!
Perhaps one could also say that the verses mention Esther’s being an orphan twice because one of those references alludes to the Jews, who complained of being left like orphans when they learned of the plot to exterminate them (Esther Rabbah 6:7).
1Rabbeinu Bachya points out in his Torah commentary that such exegesis is only made by the Rabbis when the two words are somehow related.