1A family or household; the whole family together, as in 一家そろって (all together as a family).
一家そろって温泉旅行に出かけた。
The whole family went on a hot spring trip together.
彼は一家の大黒柱として働いている。
He works as the breadwinner of the family.
台風の被害で一家は避難した。
The family evacuated because of the typhoon damage.
引っ越し先で一家は新しい生活を始めた。
The family started a new life in the place they moved to.
2To establish one's own distinct style or school in a field such as scholarship or art, as in 一家を成す (to become an authority in one's own right).
彼は書道の世界で一家を成した。
He became a master in his own right in the world of calligraphy.
長年の研究の末、彼女は独自の理論で一家を成した。
After years of research, she established her own school of thought.
3A term for a yakuza organization, likening it to a family; used attached to a group's name, as in ○○一家.
その男は地元の一家の構成員だった。
That man was a member of the local (yakuza) family.