John William Friso is the most recent common ancestor of what
John William Friso, Prince of Orange John William Friso, Prince of Orange-Nassau (Dutch: "Johan Willem Friso van Oranje-Nassau" ; 14 August 1687 – 14 July 1711) became the titular Prince of Orange in 1702. He was stadtholder of Friesland until his death by drowning in the Hollands Diep in 1711. Friso and his wife, Marie Louise, are ancestors of all European monarchs occupying the throne today.
Neithon of Alt Clut Neithon (died c. 621) was a 7th-century ruler of Alt Clut, the Brittonic kingdom later known as Strathclyde. According to the Harleian genealogies, he was the son of Guipno map Dumnagual Hen. Alfred Smyth suggests he is the same man as King Nechtan the Great of the Picts, and perhaps the Nechtan son of Canu the "Annals of Ulster" record as having died in 621. The "Senchus fer n-Alban" indicate that Gartnait, the son of Áedán mac Gabráin, King of Dál Riata, sired a son named Cano, but unless the Harleian genealogies are to be ignored, this would make Gartnait and Dumnagual Hen the same persons, as the respective fathers of Gartnait and Guipno. However, it is possible that either as an Alt Clut Briton ascending the throne of Pictland, or as a Pict ascending the throne of Alt Clut, his genealogy might have been altered, and it is notable that in the Pictish king-lists he is called ""Nechtan, nepos Uerb"", suggesting that it was a descent from Uerb that mattered in Pictland, and not his unimportant father Guipno/Canu. Alan Orr Anderson pointed out that Uerb is probably the Pictish form of "Ferb" (genitive "Feirbe"), a female name. Alan MacQuarrie suggests that Neithon was indeed the Pictish king Nechtan, but does not take any stance of the Guipno/Canu problem.