In 2009, the Office of Management and Budget’s Chief Statistician formed an Interagency Technical Working Group (ITWG) on Developing a Supplemental Poverty Measure (SPM). In March 2010, the ITWG issued a series of suggestions on how to develop a new measure drawing on the recommendations of the 1995 report of National Academy of Sciences (NAS) Panel on Poverty and Family Assistance and the extensive research on poverty measurement conducted over the past 15 years. One suggestion of the ITWG was that the family unit should be broadened to include all related individuals who live at the same address, any coresident unrelated children who are cared for by the family (such as foster children), plus cohabiting partners and their children. This paper examines how the change in unit of analysis from the family definition used in the official poverty measure (a group of two or more people residing together related by birth, marriage, or adoption) to the broader definition impacts the composition of family units. The analysis uses data from the 2010 Current Population Survey (CPS) Annual Social and Economic Supplement (ASEC).