Sentence:  America's poverty line is $63 a day for a <WSD>family</WSD> of four. In the richer parts of the emerging world $4 a day is the poverty barrier. But poverty's scourge is fiercest below $1.25 ([...]): people below that level live lives that are poor, nasty, brutish and short. 
Meaning of the word marked with <WSD> tags:  A group of people who are closely related to one another (by blood, marriage or adoption); kin; for example, a set of parents and their children; an immediate family.