OK, so according the Chicago Manual of Style, double names without hyphens should be sorted on the very last part of the name:
"In the absence of a hyphen, alphabetize by the final name. Since itís usually not possible to know for certain the origin of the name in the middle, it is treated as a middle name (not a surname) by default. Not observing this simple rule would lead to chaos: Chantelle Rutherford Smith would be listed in some directories under Rutherford and others under Smith, even if Rutherford is a middle name she was given at birth. (Note that Spanish names have their own rules; please see CMOS 16.84.)"