Who is included in a taxpayer’s family, i.e. household size?

A taxpayer’s family (household size) includes individuals for whom a taxpayer claims a deduction for a personal exemption (see IRS code:  http://www.gpo.gov/fdsys/pkg/USCODE-2011-title26/pdf/USCODE-2011-title26-subtitleA-chap1-subchapB-partV-sec151.pdf).  This may include the taxpayer, the taxpayer’s spouse, and dependents.  Dependents include a qualifying child, or a qualifying relative.  A qualifying relative is someone (1) who bears a relationship to the taxpayer, such as a father and/or mother; (2) whose gross income for the calendar year in which the taxable year begins is less than the exemption amount; (3) whom the taxpayer provides over one-half of the individual’s support for the calendar year in which the taxable year begins; and (4) who is not a qualifying child of the taxpayer or any other taxpayer.  (See IRS code: http://www.gpo.gov/fdsys/pkg/USCODE-2011-title26/pdf/USCODE-2011-title26-subtitleA-chap1-subchapB-partV-sec152.pdf)