grammaticality - The Royal Family live in mansions, or in a mansion.?

The question was in an English small test. I'm not a native speaker of English and I would like to improve my English. In this test question, we had to fill in the blanks.

Either:

1. The Royal family live in "mansions".


2. The Royal family live in a "mansion".

So the option was to put the word mansion in singular or mansions in plural.

The exersice said fill in the blank, so I asume I had to write sonething irrispect if they live in palaces.

Thanks in advance!