A person's immediate family includes his parents, spouse, children, siblings, grandparents and grandchildren. Immediate family is not restricted to biological relation; therefore, adopted, half and step members of the family are also included, as well as in-laws.
The definition of "immediate family" is very important in legal situations, as there are certain rules and regulations that pertain to immediate family members. These restrictions are set in place to ensure fairness and just treatment in certain settings. Defining "immediate family" is also important in determining tax legislation or insurance policies. Different states have different and more specific parameters for who can be considered immediate family, but the definitions are similar.