Final answer:
There are eight families that contributed to the bell tower of the Sagrada Familia in Barcelona, Spain, with four dedicated to the apostles on each façade.
Step-by-step explanation:
The bell tower of the Sagrada Familia in Barcelona, Spain, is a part of the cathedral complex that includes the Nativity Façade and the Passion Façade. The complex has a total of twelve bell towers, with four towers dedicated to the apostles on each façade. Therefore, there are a total of eight families that contributed to the bell tower.