Because his father, Tadafusa died of illness at the age of 35 years old without taking over as head of the family, Atsumaro took over as the head of the family as an adopted child of his grand father, Tadahiro KONOE (according to some historical sources, Atsumaro was the sixth son of Tadahiro).
ただし父忠房が1873年（明治6年）に家督を継がないまま35歳の若さで病没したために、祖父近衛忠煕の養子という形で家督を相続した（文献によって、忠煕六男と記しているものもある）。