For context, let me clarify. When giving ownership to a person, I can use the ’s form of that person’s name.
- This is Robert’s car.
When attributing ownership to two people or more, I can still add a final ’s after their two (or more) first names together as a unit:
- Those are Lucia and John’s cars, respectively.
Yet if I want to express ownership by people from the same family, the ’s clitic now requires the plus their last name:
- This is the Souza’s house.
So it’s safe to say that the followoed a family name always refers to collective ownership by several people.
With that said, what if I want to know the quantity of objects owned by a given family? Do I use a singular verb because it’s one single family taken as a whole, or do I use a plural verb because it’s multiple individuals?
So should I go with a plural verb like this:
- How many houses do the Souza have?
or with a singular verb like this:
- How many houses does the Souza have?
I’ve got a feeling I should go with plural do because I’m referring to more than one person (that is, to all the Souza family members), but I’d like my hunch confirmed or disputed so that I can be certain I’m doing this correctly.