Shelley, you've gone to a lot of work on my behalf and I am grateful indeed! I've continued digging online. The information you've found and what I've found does fit together, but only if there is an error somewhere, and I suspect it's the 1900 Census. The online documentation I have found also shows Annie born 15 Aug 1891 and Oscar 28 May 1889, but in the 1900 Census the dates are Sept 1890 for Annie and Oct 1889 for Oscar. Since both Bertha Fix and Ol* (looks like Olof to me) Erickson came in 1880 and have been married 40 years, it does look as though they are married to each other, but I think that MAYBE Bertha was the paternal grandmother (surname Fix) and Olof Erickson the maternal grandfather. Here's why: August's 1960 death certificate in MN gives his mother's maiden name as Erickson. There's a birth record in Washburn Co. for an Olof Harry Fix that has August's birthdate of March 31, 1887. I think this must be August, and that he later "americanized" his name from Olof. This record names the parents as Andrus (Anders?) Larson Fix and Annie Olsdatter. (It looks to me as though she were the daughter of Olof Erickson, making her an Olsdatter, but who took the name Erickson, again, americanizing a family surname. This is conjecture--maybe I've totally convoluted the information to make sense of it.
The Mrs. Fix of the 1895 census could very well be August's mother. The four males would be her sons (Andrew, August, Oscar, Emil) and the 2 females would be she herself and her daughter Annie. I assume the children's father has died between the last child (born 1891) and 1895, and Mrs. Fix dies before the 1900 Census--hence the children are with grandparents. (Bertha Fix in the 1900 Census has a child who has died.)
I'm very much hoping that stones in the cemetery can help or possibly immigration and citizenship papers. I am indeed grateful for your help and look forward to hearing from you again. Does the scenario I've described make sense to you?