This paper extends the known geographic distribution of S. tuberosum siblings recorded in 1962 by R. Landau by analyzing the polytene chromosomes in the larva. Her seven basic IIS arrangements are augmented by the addition of four new types. These were St/A, A/A; CDE-2/CDE, CDE/CDE; Y2/AB, AB/AB; and FGI. These new siblings, like the originals, have fixed differences in chromosome arm IIS. One of these, FGI, distinguished by a high degree of polymorphism, and the presence of fixed differences from the tuberosum standard in arms IS, IL, and IIIL, occurred both in Alaska and Norway. A comparison of the standard tuberosum, the S. venustum, and the FGI sibling chromosome pattern revealed the FGI sibling to be much closer to the venustum standard than any other tuberosum sibling. A second new sibling (Y2/AB) from Norway differed from the standard in the Y chromosome by multiple rearrangements in IIS and two tandem inversions in IIL. The fixed changes on arms other than IIS in the FGI siblings and the Y2/AB sibling are the first to be detected in this complex. There were a number of shared inversions in the populations studied indicating a common ancestor and (or) introgression.