On November 21, 1880, the head of the House of Hohenzollern-Sigmaringen, Prince Karl Anton of Hohenzollern-Sigmaringen, together with his sons, Carol, King of Romania, Prince Leopold and Prince Frederic, concluded the "Family Pact" by which they recognized the constitutional provisions the succession of the Romanian throne. By this act, Prince Leopold relinquished his rights of succession in favor of his sons.
Thus, according to the document, the three sons of Prince Leopold, Princes Wilhelm, Ferdinand and Carol, became from that moment "presumed heirs" of the King of Romania, Carol I.
On March 14, 1881, the legislatures approved the amendment of the Romanian Constitution, which was proclaimed a kingdom, and Prince Carol was proclaimed king. The coronation ceremony took place on May 10, 1881 and was followed by 8 days of national holiday. On this occasion, Prince Ferdinand makes his first trip to Romania, accompanying his father. Later, Ferdinand, alone or with his brother Carol, visited Romania in May 1883, May 1895 and November 1896.
After his father (in 1880) and his older brother, Wilhelm (in 1886) relinquished his rights of succession to the throne of Romania.
On November 14, 1886, Prince Ferdinand enlisted in the Romanian Army, with the rank of lieutenant in the 3rd Line Regiment.
By the resignation of his older brother Ferdinand, he unwittingly became the heir of his uncle, King Carol I of Romania. "Wilhelm, Ferdinand's older brother, tried to live in the Balkans for a year, but he found life there unsatisfactory. Preferring to live in Germany as Prince of Hohenzollern, he handed over the Romanian honors to his younger brother. Ferdinand, who lived his life longer by absence, was too weak to refuse a position that displeased him and for which he was extremely unfit. "
On March 14, 1889, the Romanian Senate voted a motion to "include in its nominal appeal the second son of A. S. R. Prince Leopold, Prince Ferdinand, with the following title" His Royal Highness Ferdinand, Prince of Romania, presumed heir to the Crown. "
On March 27, 1889, Ferdinand sent a letter from Cannes to the President of the Senate, in which he took note of the decision of the legislature and conveyed his intention to come to Romania for good, as well as his determination to carry out his duties in good faith in its new quality.
On April 17, 1889, Prime Minister Lascăr Catargiu sent for approval to the king, report no. 705, which required the approval for publication in the Official Gazette “of the 4 acts relating to the regulation of the succession to the Throne of 1880, as well as the letter of Prince Guillaume, Crown Prince of Hohenzollern, of December 29, 1886, which completes these acts. Under the Constitution, Ferdinand was not required to convert to Orthodoxy, but his descendants were expected to be baptized into the Orthodox religion.
Prince Ferdinand arrived in Romania on April 19, 1889, dressed as a lieutenant of the 3rd Line Regiment, and was greeted at the North Station by state officials, led by Royal Carol and Queen Elizabeth.
On April 23, 1889, at the suggestion of the Minister of War, Ferdinand was promoted "by choice" to the rank of lieutenant in the same regiment, whose honorary commander was his father, Prince Leopold.
