Stepfamilies and blended families are the fastest growing family types in Australia, increasing by 50 per cent over the past decade.
One in five families is a stepfamily or blended family, with experts predicting this statistic will rise as divorce rates increase and people re-partner later in life.
The number of blended families, in which children from parents' current and previous marriages live in the same household, rose by 17 per cent in the past decade, compared with just 1.2 per cent for nuclear families.
The Stepfamily Association of Victoria's Steve Martin estimates stepfamilies and blended families account for about 20 per cent of all families, including those with parents in de facto relationships.
Latest Australian Bureau of Statistics figure show there are about 175,000 blended or stepfamilies with children aged 0-17.
Step-parents are very rarely acknowledged or thanked. No one has ever called me a yummy stepmummy. There's no stepmother's or stepfather's day.
"The whole nature of the family as an institution is changing," Mr Martin said. "It comes in all sorts of forms. Many people are finding that quite confusing and distressing."
Far from a Brady Bunch image, stepfamilies and blended families confront a range of complex issues, from dealing with the breakdown of the original family to fostering a relationship between stepsiblings.
"Stepfamilies arise as a result of loss of the previous family, whether that's due to bereavement or separation and divorce," he said. "There's always a history of loss and grief.
"For adults, there's often the need to maintain a relationship with an ex-partner, no matter how fraught that may be. For children, they may not have been consulted. They may not be ready for a step-parent, they may still be hoping their parents get back together. Children need help to adjust to the new family. It's a big upheaval for everybody."
The increasing rate of family breakdown and re-partnering has put a strain on services for stepfamilies.
"Hundreds of millions of dollars are going into helping families, hundreds of millions of dollars are going into helping parents make good parenting arrangements when they separate but after that there's a desert," Mr Martin said.
More than half of parents who separate do re-partner, he said, but there was a higher breakdown rate in subsequent families, largely due to a lack of support.
National Stepfamily Awareness Day, held today, aims to encourage public support for stepfamilies.
Stepfamilies often suffer from negative assumptions, said author Dolla S. Merrillees, who has a 12-year-old stepson, Jordan, and a daughter, Shakar, aged five.
"Society perceives it as such a negative," Ms Merrillees said.
"You're battling uphill before you've even started. There are all sorts of assumptions about step-parents. People think they were responsible for the breakup of the family in the first place, which is often not the case.
"Step-parents are very rarely acknowledged or thanked. No one has ever called me a yummy stepmummy. There's no stepmother's or stepfather's day.
Many step-parents contributed to their stepchildren's lives, she said.