Rhea was Debby's grandmother and she may well have identified herself and her sisters - although I have to wonder why she did not identify her brothers as well. I suspect this picture is like so many others that gets passed down - there's no identifying information on it at all, and the identifications of the daughters may be based more on clues from other photos. Debby also has the picture of the Pape family I posted some time ago, and knew who the daughters were in that photo, but not the sons.
If three of the girls in the photo are Gertrude's daughters, I suspect the four boys are all her sons. Just based on size and age, I think they are, from left, my grandfather Paul Robert Pape (1896-1970), Walter Francis Pape (1900-1975), Otto Richard "Dick" Pape (1898-1972), and Leo John "Lee" Pape (1893-1979). Walter, the youngest, looks to be somewhere between age 2 and age 5 in this photo, meaning it was taken sometime between 1902 and 1905. It was taken, perhaps by Gertrude's husband, my great-grandfather John Pape, outside their home at 1043 Sherman in Evanston, Illinois - because the steps, porch, and front door look the same as in another photo about 15 years later.
That leaves one more girl in the picture. Who is she? She could just be an unidentified neighbor or friend.
One theory I have is that one of the girls is our elusive Emma Genevieve Pape Childs (ABT 1885-ABT 1937), the first cousin of the Pape children in this picture. If this photo was taken in 1902, she would have been about 17. Emma may have been born as late as 1887, but that would still make her older than Gertrude's oldest child, Clara. I think Emma may be the one sitting next to Gertrude. Note that they are wearing nearly the same thing - maybe they both clerked in my great-grandfather John Pape's store (Senge & Pape Dry Goods at 889 Armitage in Chicago).
Emma's parents Regina Allers and Anton Pape died in 1887 and 1893 respectively, and I think Emma was very close to Gertrude and John (she later named two of her children for them). Emma's stepmother Kate lived just down the street from John and Gertrude, at 1131 Sherman in Evanston, from at least 1895 to at least 1920.