How did a prominent family in ancient Pompeii rise to power?

The ruins of the ancient Roman city of Pompeii, a city which was absolutely perished by the eruption of mount Vesuvius, are very informative. From the remnants of the house, which belonged to the Valentes family, and from inscriptions on city's walls, we can learn how such a family gathered political power.
The interior of their house was lavishly decorated by paintings.