A step family is a family created when two families "blend." The two adults in the new family are typically marrying after divorce, becoming widowed or evolving from a single-parent status. The blending of families typically involves children of the two who are getting married, thus creating a step family.
Step families are the result of a marriage between people who have children from previous relationships. The children of these two people become step brothers and step sisters. It can be quite an adjustment for the children as well as for the parents.
Another name for step families is "blended families." It is given the name because of the way two separate families blend and become one bigger family.
It is not uncommon for step children to experience mixed emotions about their parent's remarriage and the acquisition of new brothers and sisters. As a result, behavioral problems sometimes ensue.