Thank you for the additional info, including the newspaper photo of Leslie Sr., which I hadn't seen before. It is possible that he went to Canada after his parents' deaths, although his father's immediate relatives all stayed in Minnesota and did not return to Canada themselves, as far as I can tell.
Lakewood Cemetery, where Leslie Sr. and Stella are buried, also holds nearly all of the other Ogden immigrants from Canada - Leslie Sr.'s parents, siblings, first wife, and some nephews and nieces are all buried there, as can be seen when searching the cemetery's records online.
My grandmother has passed away, as have all of her immediate relatives who would have had knowledge of Leslie. Clearly my grandma knew of him, since the notation on the back of the photo ("Leslie Ogden, February 1920") is in her handwriting. (She copied it beneath the original, identical caption done in someone else's handwriting, which had begun to fade, so clearly she wanted it to continue to be legible.)
This is really puzzling to me. I badly want to discover Leslie's fate, as his father, mother, and half-sister all died young. It would be nice to know if he lived to be an old man with children and grandchildren of his own.