This is the 16629th most frequent Russian word.
семьёй
"Семьёй" means "as a family" or "with family" in English.
In this sentence, 'семьёй' is in instrumental case, indicating companionship during the action.
Мы ужинали с семьёй в ресторане.
We had dinner with the family at the restaurant.
Here, 'семьёй' describes action performed in the context of family, also instrumental case.
Они проводят выходные в кругу своей семьёй.
They spend weekends with their family.
In this instance, 'семьёй' is used to signify possession and relation in connection to pride.