Most likely you have already noted a possible living descendant of Inger. I’ll write you a personal note, so we don’t discuss living persons in this forum.
I tried to trace Karl Johan Johansen (born 1881). Last time I could see him was 1918 in the Oslo Address Book. He was still unmarried then.
The cousins of Randi I mentioned above were all on Martha’s side of the family – no blood relation to Inger and Ivar.