Not descendants, but some little bits and pieces for you re Charles-
Helga Sundby's 1925 passenger record gave her father as Charles Sundby living at Haraldsgade 2 in Vejle. Found him at that address on the 1925 census. He is listed as 'Carl Sophus Charles Sunby' born Sept 8 1869 in Dragor (Kobenhavn). Also in that household were Maren Hansine Kirstin born May 21 1868 in Barrit (2nd wife?) and Oda Else, born Aug 31 1919 in Aarhus. (I did look at Oda's birth record - she was born to unmarried Thora Marie Moller and adopted by Carl Sophus Charles Sundby and Maren Johanne Kirstine Hansine nee Hansen. And I checked Maren's birth record - 'Maren Johanne Kirstine Hansine Hansen' is her correct name.
Found a birth record for 'Carl Sophus Charles Sundby in the Skt Johannes (Kobenhavn) parish record. Born Sept 8 1869 to Jakob Helge Sundby and Marie Sophie nee Nielsen.
And found his family on the 1880 Census for Aagade, Kobenhavn
Helge Sundby 40 Maskinarbejder, husfader b. København
Sofie Marie f. Nielsen 37 Hans kone b. Gladsaxe, København
Charles Sofus Sundby 10 Deres søn b. København
Thor Sundby 9 Deres søn b. København
Emil Hakon Sundby 7 Deres søn b. København
Fanny Caroline Sundby 4 Deres datter b. København
Hope this helps,