in which scenarios would one have 'stepfamilies'?
A step family is a family where at least one parent has children that are not biologically or adoptive related to the other spouse or partner. Either parent, or all, may have children from previous relationships.
Stepfamily
A step family, blended family, bonus family, or instafamily is a family where at least one parent has children that are not biologically or adoptive related to the other spouse or partner. Either parent, or all, may have children from previous relationships. Children in a stepfamily may live with one biological or adoptive parent, or they may live with each biological or adoptive parent for a period of time. In addition, visitation rights mean that children in stepfamilies often have contact with both biological parents, even if they permanently live with only one.

A child is referred to as the stepdaughter or stepson of their biological or adoptive parent's new spouse, and that person as the stepparent, father or mother of the child.

A stepparent is the spouse of someone's parent, and not their biological or adoptive parent, being stepfather the male spouse and stepmother the female spouse. 
A step-grandparent is not someone's biological or adoptive grandparent, being stepgrandfathe
most common type of family in the us Single-parent homes in America are increasingly common. what are the different types of family structures in the united states? The traditional family structure and alternative family forms what is meant by a 'nuclear family'? The nuclear family consists of a mother, father, and the children
wiki:19481580
Stepfamily [SEP] Introduction
A step family, blended family, bonus family, or instafamily is a family where at least one parent has children that are not biologically or adoptive related to the other spouse or partner. Either parent, or all, may have children from previous relationships. Children in a stepfamily may live with one biological or adoptive parent, or they may live with each biological or adoptive parent for a period of time. In addition, visitation rights mean that children in stepfamilies often have contact with both biological parents, even if they permanently live with only one. A child is referred to as the stepdaughter or stepson of their biological or adoptive parent's new spouse, and that person as the stepparent, father or mother of the child.