Ferdinand I (1865-1927) and Marie of Saxe-Coburg-Gotha (1875-1938)

[CyrilVladisla]

Prince Ferdinand of Hohenzollern-Sigmaringen was adopted as crown prince of Romania in 1889 by his uncle King Carol I.
Was it a requirement that Prince Ferdinand had to be adopted?

 

[Blog Real]

The Balkan Crown Princes at a gathering: Alexander of Serbia, Boris of Bulgaria, Constantine of Greece, Ferdinand of Romania and Danilo of Montenegro in 1912.

https://c4.quickcachr.fotos.sapo.pt/i/G5d170f05/22625603_mHsb1.jpeg