Grandparents are considered a part of an immediate family. Immediate family is usually defined as one's spouse, parents, grandparents, children, grandchildren, siblings and immediate in-laws (mother-in-law, father-in-law, brother-in-law and sister-in-law). Adopted children and stepchildren also count as immediate family members.
Generally, there are two ways to determine who are considered immediate family members. The first is relationship by blood, meaning that they share the same parent or lineage, as in the case of children, grandchildren or siblings. The second is being related by marriage, as with stepchildren and in-laws. Aunts, uncles, nephews, nieces and cousins start to move away from immediate family.