At present, who is considered to be part of the imperial family?

The only people who as members of the imperial family can marry and hold the title -miya (prince or princess), are the children of the Emperor.
Accordingly, as of September 2004, those considered to be members of the imperial fanlily are: the Emperor and Empress; the Crown Prince and Princess, their child Princess Toshi; Prince and Princess Akishino, their two children; Princess Nori; the brother of the Heisei Emperor (Prince and Princcss Hitachi); the brothers of the Showa Emperor (Prince and Princess Mikasa) and the wife of the late Prince Takamatsu; the children of Prince Mikasa (Prince and Princess Tomohito) and their two children, Prince Katsura, the wife of the late Prince Takamado and their three children.
The status, rights, and responsibilities of the imperial family are stipulated under the Imperial Household Law, but imperial family members are subject to the same laws governing regular citizens.
The only difference is that they do not have family registers.
Also, there is no required surname for the imperial family.
The name of the Crown Prince is simply Naruhito; Owada Masako, who became the Crown Princess, is simply called Masako.
When an imperial fanlily name is accorded, this serves as the surname.