Today is the feast of St. Hermenegild, eldest son of Levigild, the Visigothic king of Spain, and his first wife, Theodosia. Levigild shared his kingdom with his sons, placing Hermenegild on the throne at Seville.
Hermenegild and his brother Recared were Arians like their parents and like their stepmother, Gosvint, but when Hermenegild married Ingondes, a Catholic, her example and the "instructions and exhortations of St. Leander, bishop of Seville" caused the Arian Hermenegild to be "received into the church by the imposition of hands, and the unction of chrism on the forehead".
Levigild was enraged by his son's conversion and "divested him of the title of king, and resolved to deprive him of his possessions, his princess, and even his life, unless he returned to his former sentiments".
Instead of returning to Arianism, Hermenegild revolted against his father, seeking support from the few Catholics in Spain, from the Roman remnants, and from Constantinople. But the revolution failed, and Levigild had him "stripped of his royal robes, loaded with chains, and conducted prisoner to the tower of Seville".
On the eve of Easter, April 13, 586, the king sent an Arian bishop to Hermenegild's cell, "offering to take him into favour, if he received the communion from the hand of that prelate, but Hermenegild rejected the proposal with indignation".
Then the king sent soldiers who "found the saint fearless and ready to receive the stroke of death, which they instantly inflicted on him, cleaving his head with an axe, whereby his brains were scattered on the floor. St. Gregory the Great attributes to the merits of this martyr, the conversion of his brother, king Recared, and of the whole kingdom of the Visigoths in Spain".
Even his father "was stung with remorse for his crime" and "on his death-bed, he recommended his son Recared to St. Leander, desiring him to instruct him in the same manner as he had done his brother Hermenegild, that is, to make him a Catholic".
-- http://books.google.com/books?id=YHgTAAAAQAAJ&pg=PA135&lpg=PA135&ots=3e24OrbwGt&dq=st.+hermenegild&ie=ISO-8859-1&output=html> The Lives of the Fathers, Martyrs, and Other Principal Saints, by Alban Butler, 1821
Modern historians raise tantalizing questions about Hermenegild's revolution, particularly about the role of the women, the Arian Gosvint and the Catholic Ingondes, but they do not dispute the accounts by St. Gregory the Great and St. Gregory of Tours. See, e.g., Visigothic Spain 409 - 711,  by Roger Collins, Wiley-Blackwell, 2004. Search term: Hermenegild.
Click here  to see the painting of St. Hermenegild by Francisco de Herrera.  The martyr is depicted ascending into heaven. St. Leander, with Hermenegild's son, is on the left, and Leander's brother, St. Isidore, is on the right. King Levigild "kneels with averted face".