In 1534, he married
Isabella Colonna of the prominent
Colonna family. The widow of
Louis "Rodomonte" Gonzaga, Isabella was the only daughter of
Vespasiano Colonna, Duke of
Traetto, Count of
Fondi, and, his first wife, Beatrice
Appiani. She was raised, however, by her father's second wife,
Giulia Gonzaga. From her first marriage, she was the mother of
Vespasiano I Gonzaga, who became the
Duke of Sabbioneta. Together, they were the parents of five children: • Maria de Lannoy, who became nun in the monastery of
Santa Maria Donna Regina in Naples. •
Charles de Lannoy, 3rd Prince of Sulmona (1538–1566), also 2nd Count of Venafro; he married Costanza Doria
del Carretto. • Beatrice de Lannoy, who married Alfonso de Guevara, 5th Count of Potenza. After his death, she married Alberto
Acquaviva d'Aragona, 12th Duke of
Atri. •
Horace de Lannoy, 4th Prince of Sulmona (d. 1597), also 3rd Count of Venafro; he married Antonia
d'Avalos. The Prince died in 1553 and was succeeded as Prince of Sulmona by his eldest son,
Charles. The title, however, became extinct upon the death of Philip II de Lannoy, 6th Prince of Sulmona in 1604. Upon his widow's death at
Naples in 1570, her son Vespasiano from her first marriage inherited all her possessions. ==Notes==