Last month, my wife and I took a vacation to Madrid. While Spanish is my wife’s largest “pre-1492” ethnic background (the others being African and Native-American), I have yet to trace an ancestor who was actually born anywhere besides the Dominican Republic. The furthest I’ve gone is to an ancestor born about 1713, who appears on an 1812 census in her father’s hometown of San Francisco de Macoris. (See this post for information on some of my wife’s Dominican Republic ancestry.)
However, through a few of my own documented “royal” lines, I end up with a few cases of Spanish ancestry through my colonial British forebears. On our trip to Madrid, we walked through the Buen Retiro Park and outside the Royal Palace of Madrid, both of which have numerous statues of rulers of various Spanish kingdoms (Castile, Aragon, Leon, Barcelona, etc.), as well as monarchs after unification with the marriage of Ferdinand and Isabella. On a day trip to Segovia, we also saw the Alcázar, which has the Hall of Kings with painted statues of early monarchs of Castile ending with “Juana la Loca,” the well-known daughter of Ferdinand and Isabella and mother of Emperor Charles V.
The easiest way for most people with Colonial American ancestry to connect (via the British royal family) back to early Spanish rulers is through Eleanor of Castile, the wife of King Edward I of England. Two works – Royal Ancestry by Douglas Richardson, and the forthcoming updated The Royal Descents of 900 Immigrants by Gary Boyd Roberts – are useful in determining these connections. While this is by no means one of my genealogical specialties, I’ve enjoyed seeing these various lines of descent for my own ancestors.
Roberts’ work is getting updated this year, and so I decided to demonstrate (on the chart below) the way many of the immigrants he includes would have connections to earlier rulers of pre-union kingdoms of Spain. This chart does not outline all Castilian descents (there are indeed many more!), but it shows how the most recent couples’ various royal lines may begin in Roberts’s work, treating the most recent Spanish marriage (for this reason I also include Isabella of Castile as the wife of Edmund of Langley).
In Roberts’ work, before he covers the immigrants descended from Edward III, he reviews those immigrants with descents from more recent kings, i.e., from King Edward IV of England to King Ferdinand I of Romania (died 1927). The large majority of these kings will also descend from Eleanor of Castile and thus share the above ancestry.
The other way many British people and Americans of British descent derive Spanish descent is through Sancha de Ayala, the Spanish wife of Sir Walter Blount, which provides an even closer connection to later kings of Spain, as Sancha’s brother was the great-great-grandfather of Ferdinand, husband of Isabella. However, nearly all American descendants of Sancha de Ayala will also end up with these earlier Castilian connections, as Sancha herself likely descends from King Alfonso VI above. Sancha’s American immigrant descendants go through her children Thomas and Constance. Constance Blount married Sir John Sutton, who was a descendant of Eleanor of Castile and Edward I. In the 2015 update to the 2012 reprint of Ancestors of American Presidents, Roberts lists 50 American immigrants who descend from Sancha de Ayala, most of whom also descend from Eleanor of Castile.
Also on the chart above is Philippa of Hainault, wife of King Edward III of England, who was a great-great-granddaughter of King Jaime I of Aragon (died 1276). This new edition of Roberts includes one rather interesting descent back to Jaime I. The immigrant to the American continents is Alonso Riquelme de Guzman of Paraguay, whose daughter Catalina moved to Argentina.
After several Argentine generations, a descendant – Francisco de Paula Lynch Zavaleta (1817–1886), moved to San Francisco during the Gold Rush. Francisco’s daughter returned to Argentina and was the grandmother of Argentine-born Cuban and Bolivian revolutionary leader Ernesto “Che” Guevera de la Serna (1928–1967). I found this descent online and this was subsequently verified by NEHGS member Thomas Gede. Certainly more such lines likely exist to immigrants in Latin America; thus, many people from parts of the former British and Spanish empires may share not-too-distant kinships.
 For lines that descend from the sons of Edward I by his second wife, Marguerite of France, Marguerite was a great-great-granddaughter of Alfonso VIII, King of Castile, grandson of Alfonso VII on the chart.
 For more information on Sancha de Ayala, see Milton Rubincam, “The Spanish Ancestry of American Colonists,” National Genealogical Society Quarterly 51 : 235–38; Nathaniel L. Taylor and Todd A. Farmerie, “Notes on the ancestry of Sancha de Ayala,” Register 103 : 36–48 (an online version of this last also appears here); and the above update by Roberts.