'Royal house' in the Bible

Also Vashti the queen made a feast for the women in the royal house which belonged to king Ahasuerus.

So Esther was taken unto king Ahasuerus into his royal house in the tenth month, which is the month Tebeth, in the seventh year of his reign.

And it cometh to pass on the third day, that Esther putteth on royalty, and standeth in the inner-court of the house of the king over-against the house of the king, and the king is sitting on his royal throne, in the royal-house, over-against the opening of the house,