This cabinet card features adorable siblings posing for their portrait at the Setzer studio in St. Louis, Missouri. The photographer is Theodore E. Setzer. Setzer operated his studio from the South Broadway address from about 1890 until 1910, according to one photographer reference book. Between 1885 and 1890 he conducted business from that address as Setzer & Roth.
THE CABINET CARD GALLERY 
They are indeed adorable. I wonder how often that little boy had to be dressed up like that.