'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 to King Ahasuerus into his royal house in the tenth month, which is the month Tebeth, in the seventh year of his reign.

Now it happened on the third day that Esther put on her royal clothing, and stood in the inner court of the king's house, next to the king's house. The king sat on his royal throne in the royal house, next to the entrance of the house.