In ancient times, in Bible times, kings only ascended the throne after being consecrated with the "holy oils" in the name of God. Thus the peoples knew that they ruled them by "divine right".
So it was with Saul, the first king of Israel, who was anointed by the prophet and judge Samuel. So it happened also to his successor, King David.
After the destruction of the 2nd Temple of Jerusalem by the Roman Emperor Titus, there was never again a king in Israel. In the Bible it is written that when the Kingdom of Israel is restored, its king will be a descendant of the House of David, who will be anointed (Machiah in Hebrew, Messiah in English or Christs in Greek, all this means "anointed").
A moment before the destruction of Jerusalem, Rabbi Yohanan ben-Zacai managed to leave the city, with the consent of the Romans, and went to establish Sanhedrin (council of elders, a kind of parliament) in Yavné. Obviously, it became convenient to declare that Yohanan ben-Zacai was a descendant of King David. Perhaps even so. It is difficult to prove it or contest it. Therefore he assumed the spiritual power of the people by hereditary right.
Davidic hegemony continued in the Jewish academies of Babylon, whose chiefs, as descendants of the anointed king David, assumed the title of "nassi", prince.
When the Jew Jesus was proclaimed Messiah (Christ) by the faith of his followers, it was soon declared that Joseph, his human father, was a descendant of King David.
It follows that many European dynasties presented themselves as descendants of the same king of Israel, and therefore their kings sat on the throne, by divine right, consecrated in the Bible.
When Pepino de Herstal died in December 714, his illegitimate son Charles Martel (Hammer) assumed the power of the kingdom of the Franks. But he never proclaimed himself king.
He did, however, assume a winning strategy. Abraham Ibn-Daud, himself a descendant of King David, and a renowned historian, tells in his main work, "Sefer HaKabalah" (Book of Kabbalah) that Charles wrote to the Caliph of Baghdad asking him to send one of his Jews, "to carry within himself the seed of royalty from the house of David".
Ibn-Daud attributed this initiative to Charlemagne, but historians believe it was confusion on the part of the author, who wrote his work around 1161. And that it is in fact Charles Martel, the initiator of the Carolingian dynasty.
The caliph sent him a wise man and a Babylonian magnate named "Makir", son of Natronai, Exilarca of Pumbedita.
In 721, Charles Martel defeated the Muslims in the Battle of Tours (also known as the Battle of Poitiers), which was the beginning of the end of the Arab presence in Europe. Then he handed over the conquered lands to the Muslims in Narbona to Makir, who, also with the title of nassi, there created a Jewish principality and a yeshivah (rabbinical academy).
In addition, Charles Martel married the Jewish sage to his daughter Alda (also known as Aldana), whose brother, Pepino, the brief, took the throne on the death of his father. The marriage of a Jew to a Gentile, and a noble Carolingian to a Jew, is problematic, and seems to imply the conversion of Makir. But the goal of planting the seed of royalty from the house of David in the Carolingian royal family was achieved.
From this marriage was born a son named William (Wiliam), whose father entered the annals of history under the name Theodoric, which led historian Arthur Zuckerman (A Jewish Princedom in Feudal France) to conclude that Makir was baptized under the name Theodoric, beginning a dynasty of French-Jewish kings in Narbona. This represents the union of the lineage of the exiles of Pumbedita with the Carolingians, descendants of Charles Martel.
This son was known as William of Gellone, or Aquitaine, and later as Count of Toulouse or William of Orange.
From this William are descended the monarchs of the Kingdom of Portugal, with the exception of those of the Philippine dynasty.
Count Henry was the fourth son of Henry of Burgundy, grandson of Robert I, Duke of Burgundy, great-grandson of Robert the devotee, King of France, third grandson of Hugo Capeto, King of France, fourth grandson of Hugo the great, Duke of France, fifth grandson of Roberto II, Duke and Marquis of France, then King, sixth grandson of Roberto I, the fort, Duke and Marquis of France.
According to custom at the time, the French nobles, not being first-born, were unlikely to have access to their parents' titles. The only solution for most of the younger children of European noble families was to place themselves in the service of foreign kings, in order to obtain other honorary titles and their incomes.
The Spanish king offered them this opportunity. Henry of Burgundy and his cousin Raimundo, placed themselves at the service of Alfonso VI of Castile.
Therefore, if we accept the genealogy based on family tradition, the first king of Portugal, Alfonso Henriques, was a descendant of King David of Israel.
Circumstantially, also the Jew Yahia ben Yaish, the first major of Portugal, and a collaborator of King Afonso Henriques in his conquests of the Muslims, was a descendant of King David.
Just as he was the Master of Aviz, then D. João I, whose illegitimate son, from his connection with the Jewish Inês, daughter of the Barbadão da Guarda, was the first Duke of Bragança, D. Afonso.
The present Duke of Bragança. S. A. D. Duarte Pio, pretender to the throne of Portugal, is doubly descended from Jews. And when he visited the Holy Land on pilgrimage in 2006, he did not fail to mention to his Israeli hosts his Davidic ancestry.
King Afonso Henriques is the direct grandfather of Lord Lamont Couto d' Chandos, being the supreme Lord Lamont Couto d' Chandos descendant of King David by the line of his grandfather King Afonso Henriques of Portugal.