The children Daniel and Alice are living with Harriet's sister, Ordelia, in 1900. That probably means both Harriet and Andrew died before 1900.
Carl first appears in Daniel's household in 1920, listed as a brother, shortly after Daniel left his first wife and married Lulu. He keeps the name Strebel in 1930, though, so maybe he really is a brother rather than an army buddy going under an alias. But he wasn't with Daniel and Alice when they lived with Ordelia in 1900.
Here's a picture of the siblings Sarah, George, and Harriet (from Thomas Reel)
