Fetching details from the dictionary...
(present) head of a family
当主が遺産を相続した。
The head of the family inherited the estate.
旧家の当主は重い責任を担っている。
The head of the old family carries a heavy responsibility.
老舗の当主が急逝し、番頭が暫定的に経営を引き継いだ。
The head of the long-established business died suddenly, and the chief clerk temporarily took over management.