According to the existing Imperial House Act, the Emperor's legitimate son as well as grandchildren from his legitimate male-line descendants are called Imperial Princes and Imperial Princesses; descendants beyond the Emperor's grandchildren (third generation) from his legitimate male-line descendants are called Princes and Princesses (Article 6 of the Imperial House Act).
現行の皇室典範では、嫡出の皇子及び嫡男系嫡出の皇孫が親王・内親王とされ、三世以下の嫡男系嫡出の子孫は王・女王とされる（皇室典範6条）。