Germany
Louis Ferdinand Prinz von Preußen, 1907-1994
NB. His son Prinz Friedrich Wilhelm (1939-2015) would be more appropriate to put in this slot, but he seems to still be listed as living on Wikitree.
Out of 2046 possible ancestors in 10 generations, 1348 (65.88%) have WikiTree profiles [previously 62.41%]. 799/1348 (59.27%) are duplicates due to pedigree collapse. His three most recent ancestors missing one or both parents are:
* Luise Karoline Geyer von Geyersberg, 1768-1820 shared with Denmark and Sweden
* Ernst August von Sachsen-Weimar-Eisenach, 1737-1758
* Gräfin Ernestine von Schönburg-Wechselburg, 1736-1768
Great Britain
George VI, King of Great Britain, Ireland, &c. (1895-1952)
Out of 2046 possible ancestors in 10 generations, 1220 (59.63%) have WikiTree profiles [previously 59.04%]. 724/1220 (59.34%) are duplicates due to pedigree collapse. His three most recent ancestors missing one or both parents are:
* Marie Luise Freiin von Wallenrodt, * c.1734
* Borbála Henter de Sepsiszentiván, * before 1725
* Ágnes Vass de Diód-Váralja, * before 1720
If, however, you're of a more quixotic and Jacobite turn of mind, you might prefer,
Albrecht, Herzog von Bayern (1905-1996), the most recently deceased Jacobite pretender.
Out of 2046 possible ancestors in 10 generations, 1389 (67.89%) have WikiTree profiles [previously 65.4%]. 844/1389 (60.76%) are duplicates due to pedigree collapse. His three most recent ancestors missing one or both parents are:
* Louis-Joseph-Augustin de Mailly-Rubempré, 1744-1810
* Ernestine Auguste Sophia Prinzessin von Sachsen-Weimar-Eisenach, 1740-1786
* Johann Christian Graf zu Solms-Baruth, 1733-1800
Italy
Umberto II, King of Italy (1904-1983)
Out of 2046 possible ancestors in 10 generations, 824 (40.27%) have WikiTree profiles [previously 38.27%]. 565/824 (68.57%) are duplicates due to pedigree collapse.His three most recent ancestors missing one or both parents are:
* Petar Vukotic (1826-1907)
* Jelena Vojvodic, * c.1825
* Stana Martinović (1824-1898)
Liechtenstein
Franz Joseph II Fürst von Liechtenstein (1906-1989)
Out of 2046 possible ancestors in 10 generations, 883 (43.16%) have WikiTree profiles [previously 40.91%]. 433/883 (49.04%) are duplicates due to pedigree collapse. His three most recent ancestors missing one or both parents are:
* Maria Josepha Sophia von Fürstenberg-Weitra, 1776-1848
* Rudolf von Wrbna und Freudenthal, 1761-1823
* Dorota Barbara Jablonowska, 1760-1844