Two and a Bit by Vernon Stokes and Cynthia Harnett. A charming book this from 1948 tells the story of a brother and sister, who get on so well they might as well have been twins (like all siblings in the 1940s of course) and their little dog, the 'half' of the title. Judging by the initials, it seems that Vernon Stokes did most of the drawing but that they collaborated on some of it.
