About the conecction with the Duke of Alba I must say that there is no links of blood between the people surnamed Alba and his family; in fact, the origin of the Alba surname is earlier than the first Duke of Alba. The Duke of Alba is a title of nobility and not a surname, it was given because of a spanish village called Alba de Tormes (Salamanca). In 1429 Juan II, king of Castille, gave the village to the bishop Gutierre Alvarez de Toledo with the title of Lord. He was succeeded by his nephew Fernando Alvarez de Toledo, who was given the title of Count in 1438. His son, Garcia, received in 1472 the first title of Duke of Alba. Maybe later a family could inherit the surname of Alba from the Dukes, I don´t Know, but it is sure that the origin of most Albas isn´t that; and it´s even probably that the village, Alba de Tormes, was founded by someone surnamed Alba during the Reconquest.
Hoping it could help some of you and waiting for new info about our roots, Maria Alba, sister of Pilar Alba