'Royal house' in the Bible

Also Vashti the queen, made a banquet for the women, - in the royal house which belonged to King Ahasuerus.

So then Esther was taken unto King Ahasuerus, into his royal house, in the tenth month, the same, was the month Tebeth, - in the seventh year of his reign.

And it came to pass, on the third day, that Esther put on her royal apparel, and stood in the inner court of the house of the king, over against the house of the king, - and, the king, was sitting upon his royal seat, in the royal house, over against the opening of the house.