His wife was active too
https://www.marxists.org/archive/duncker-kate/index.htm
As there was an earlier exchange on the forum about women, she writes about it in 1910
https://www.marxists.org/archive/duncker-kate/1910/women-social-democracy.htm
“…it is clear that there is only one means for the women of the proletariat to free themselves from wage and domestic slavery and to fight for equal rights, namely by joining the ranks of the Social Democratic struggle. Even if they cannot yet cast their votes for Social Democracy in the elections, they can still join the Social Democratic organization and work in it…And if women join the Social Democrats in ever-increasing numbers, the latter will not only grow in size, but their clout and confidence in victory will also increase. The man who has an unenlightened and indifferent wife at home is only half a fighter, an uncertain one…”
https://www.marxists.org/archive/duncker-kate/1910/women-social-democracy.htm