Our, us, we can always refer to (addressee is the person spoken to):
- the speaker and and the addressee
- the speaker and a third party
- the speaker, the addressee and a third party
Some languages have different words for an us that includes the addressee or not.
In the case of "our family", it is not strange that someone would refer to their family in that way. I could tell you, or a stranger, about "our family", meaning "my family", not yours:
In our family we always married inside the family: my father married my mother, my uncle married my aunt, and my grandfather married my grandmother.
My family would surely also be correct, but some speakers prefer to use our.
I have heard people refer to our house in the same way. It is as if the speaker is not only speaking for themself, but also for the rest of the people involved:
We, members of the Johnson family, think our family is a good family. Our family is great!
We, the owners or occupants of that house, like our house a lot. Our house is lovely!
Even when only one person of the group is present, they can speak from that perspective, meaning exactly the same:
I think our family is a good family. Our family is great!
We like our house. Our house is lovely!
The same thing happens when your friend tells you about his football team:
Our team is doing great! We won the last five matches!
That does not mean you are part of that team!