Complex sentence: His father was Juan Pérez de Narriahondo--who changed his name in later life to "Juan de Oñate"--and his mother was Osana González de San Llorente.
Split into simpler sentences: His father was Juan Pérez de Narriahondo, who changed his name in later life to "Juan de Oñate". Oñate's mother was Osana González de San Llorente.