你的问题不明白.这句话首先不对,应该是：It is your turn to clean room.这句话it是形式主语,真正的主语是不定式to clean room.也就是To clean room is your turn.为了避免头重脚轻 才用it做形式主语.
还是你要写成It is his turn to clean room或者It is their turn to clean room.
都是对的.主语it,后面一直用is.