Someone related to the taxpayer by blood, marriage, or adoption, including the following:

  • Child, grandchild, great grandchild
  • Stepchild, stepbrother, stepsister
  • Brother, sister
  • Half-brother, half sister
  • Parent, grandparent, or other direct ancestor (but not foster parent)
  • Stepmother or stepfather
  • Brother or sister of one’s father or mother
  • Son or daughter of one’s brother or sister
  • Father-in-law, mother-in-law, son-in-law, daughter-in-law, brother-in-law, or sister-in-law.