It was said in the context that very different parenting styles was a major factor in follow-on marriages failing. If one parent is very different from the other, stress results - a parent having to side with their kids or their new spouse.
They brought it up to recommend that this be a topic of discussion before you decide to live together or M.
I don't know if this is a major factor in failed marriages or not across the board, but it makes sense to me. My parenting style (or lack of) vice my former W's style (way too involved) contributed greatly to the end of my M and my M was not a blended family.
