Blended families now outnumber first families in both the US and the UK and Carr-Gregg reckons New Zealand and Australia are following suit.
So, with blended families now the norm, how do parents make sure they are doing things right? Are there support groups and parenting courses to guide them? And should couples consider marriage guidance and counselling when they get together rather than only as a last resort when relationships start to show cracks?
Perhaps the answer is in one of Carr-Gregg's comments. He remembers TV's Dr Phil saying that if you are a psychologist with an area of specialty and you don't write self-help books, then you're crazy ... because the vast majority of people won't darken psychologists' doors. There is still a stigma about going and getting help.
He reckons step-parenting is one of the toughest gigs around. "It is not fun. The desperation, the depth and breadth of misery that doing it wrong can cause really does take away, for many people, a quality of life and they can become desperate.
"Given that we have so many parents separating and divorcing, why isn't there mandatory free marriage guidance counselling beforehand? The Catholic Church, I believe, offers that to couples about to wed. Certainly, there is a bit of a movement in Australia to put those services on the public purse."
Carr-Gregg says step-parenting is different from biological parenting. It is less spontaneous, requires more patience, effort, resilience and stamina. But he also reminds step-parents having problems not to blame it all on being a step-family as all families experience stressful times.
"The most important thing to understand is that, universally, the first two years are purgatory. There is no getting around it," he says, "and you have to basically gird your psychological loins for that. Don't expect things to be perfect. There will be arguments, there will be some fairly robust exchanges, particularly with teenagers. You have to prepare yourself, have the answers for the questions like: "You're not my father, you can't tell me what to do" (Michael's favourite answer: "I'm the only one you've got here at the moment and we have to make do"). Another important piece of advice is for parents to invest in their own relationship, based on good communication, trust and respect.
"The tendency is to cater for everybody else's needs and that doesn't work."
Recognise that this not going to be an instant family, Carr-Gregg says. This will take time. Research has shown step-families have their own natural stages: fantasy (similar to a honeymoon period), then confusion followed by conflict, before moving on to resolution and comfort.
But there are also many examples of happy step-families. And there is help at hand. He suggests joining step-parent associations and chatting to people who have been down this path. "The difficulty is many people are time poor. That is why I wrote the book, Surviving Step-Families. It is little, it's readable and it's distilled in plain English without psychobabble."
Perhaps his book should be in every step-family's stocking this Christmas.
Tips:
* Keep things simple; stay within your budget
* Plan ahead and communicate well
* Holidaying and travelling together strengthens bonds
* Remember - you are not the parent
* Don't personalise things
* Don't neglect your marriage
"Step-parents should not try to be the parent - this is the death knell. The step-parent needs to take a position of one down. They need to support the biological parent in the disciplinary role, they need to allow the relationship to develop over time. You will never take over the role of the child's biological parent, nor should you." - Michael Carr-Gregg
* Surviving Step-Families, by Michael Carr-Gregg ($26, Penguin).