There are historical examples of individuals who became monarchs before their birth. This occurred primarily due to specific circumstances, such as the death of a reigning monarch and the lack of a direct heir.
One notable example is Shah Shapur II of the Sassanid Empire. According to legend, he became king before his birth because his father, Shapur II, died before he was born. The queen, who was pregnant at the time, was crowned, and her unborn child was declared king.
Other instances involve individuals who were declared heir to the throne before their birth, ensuring their future claim to the monarchy. This was the case with Alfonso XIII of Spain, who was named king on the day of his birth in 1886.
While these are just a few examples, the concept of becoming king before birth is intriguing and highlights the complexities of historical succession.