Karl Friedrich, Prince of Hohenzollern
Karl Friedrich, Prince of Hohenzollern (born 20 April 1952) is the eldest son of the late Friedrich Wilhelm, Prince of Hohenzollern and Princess Margarita of Leiningen.
He became head of the Princely House of Hohenzollern, the Roman Catholic Swabian branch of the dynasty, upon his father's death on 16 September 2010.
Heinrich Donatus, Hereditary Prince of Schaumburg-Lippe
Heinrich Donatus, Hereditary Prince of Schaumburg- Lippe( Ernst- August Alexander Wilhelm Bernhard Krafft Heinrich Donatus; born 13 May 1994) is the son of Alexander, Prince of Schaumburg- Lippe and thus heir to the German Princely house of Schaumburg- Lippe.
Prince Heinrich Donatus of Schaumburg- Lippe was born in Hanover to Alexander, Hereditary Prince of Schaumburg- Lippe( born 1958), and Princess Marie- Louise(" Lilly") of Sayn- Wittgenstein- Berleburg( born 1972), who had married in August 1993.
His mother suffered a nervous breakdown in 1998, and left her husband in 2000 to move with her son from Hanover to Munich.
The couple divorced in 2002.
On the death of his father, Philip- Ernst, Prince of Schaumburg- Lippe, Alexander inherited the title Prince of Schaumburg- Lippe, while his son became Hereditary Prince.
In 2007, the Prince of Schaumburg- Lippe married lawyer Nadja Anna Zsoeks.
Princess Marie- Louise is now married to designer Lambros Milona, with whom she has a daughter, Lana.
Alexander, Hereditary Prince of Hohenzollern
Alexander, Hereditary Prince of Hohenzollern (born 16 March 1987 in New York City) is a member of the Princely House of Hohenzollern.
Alexander is the eldest son of Karl Friedrich, Prince of Hohenzollern and Countess Alexandra Schenck von Stauffenberg, who divorced in 2010.
He is the heir apparent to the headship of the princely house.
Peter, Hereditary Prince of Yugoslavia
Peter, Hereditary Prince of Yugoslavia( born 5 February 1980), also known as Peter III Karađorđević(/" Petar III Karađorđević"), is the eldest son of Alexander, Crown Prince of Yugoslavia, and Princess Maria da Gloria of Orléans- Braganza.
Prince Peter is the grandson of King Peter II.
Peter, Hereditary Prince of Yugoslavia' is second in line after his father HRH Crown Prince Alexander to the defunct throne.
Frederick, Prince of Hohenzollern
Frederick, Prince of Hohenzollern( 30 August 1891 in Heiligendamm, Mecklenburg- Schwerin – 6 February 1965 in Krauchenwies, Baden- Württemberg, Germany) was the eldest son of William, Prince of Hohenzollern and Princess Maria Teresa of Bourbon- Two Sicilies.
He had a twin brother, Franz Joseph, Prince of Hohenzollern- Emden, who was born a few minutes after he was.
Frederick XI, Count of Hohenzollern
Friedrich XI, Count of Hohenzollern( died 26 November 1401), nicknamed" Friedrich the Elder" was a German nobleman.
He was a member of the House of Hohenzollern and a ruling Count of Hohenzollern- Hechingen.
Friedrich Wilhelm, Prince of Hohenzollern
Friedrich Wilhelm, Prince of Hohenzollern( 3 February 1924 – 16 September 2010) was the head of the Princely House of Hohenzollern for over 45 years.
Maximilian I, Prince of Hohenzollern-Sigmaringen
Maximilian I, Prince of Hohenzollern- Sigmaringen( 20 January 1636 – 13 August 1689 in Sigmaringen) was a German nobleman.
He was the third ruling Prince of Hohenzollern- Sigmaringen; he ruled from 1681 until his death.
Prince Karl Anton of Hohenzollern
Prince Karl Anton of Hohenzollern- Sigmaringen( 1 September 1868 – 21 February 1919) was a member of the Princely House of Hohenzollern- Sigmaringen.
Karl Anton was the third and youngest son of Leopold, Prince of Hohenzollern and his wife Infanta Antónia of Portugal.
Karl Anton's elder brothers were William, Prince of Hohenzollern and Ferdinand I of Romania.
Constantine, Prince of Hohenzollern-Hechingen
Constantin, Prince of Hohenzollern- Hechingen( Friedrich Wilhelm Konstantin Hermann Thassilo; 16 February 1801 – 3 September 1869), was the last Prince of Hohenzollern- Hechingen.
Constantine was the only child of Frederick, Prince of Hohenzollern- Hechingen and his wife, Princess Pauline of Courland, the daughter of the last Duke of Courland, Peter von Biron.

Question: Who is the paternal grandfather of Alexander, Hereditary Prince Of Hohenzollern?
Answer: Friedrich Wilhelm, Prince of Hohenzollern