In Europe, regardless of male-line or female-line, only children who were born between royal families (including royal family members from other countries and prosperous peerage) have been allowed to ascend to the throne.
ヨーロッパでは男系であれ女系であれ、代々王族同士（他国の王族ないしこれに準ずる有力貴族を含む）の間に生まれた嫡子のみに王位を継承させていた。