The Wall Street Journal reported that 40% of the U.S. population has at least one step relative and 30% have a step or half sibling. Research suggests that it can take at least ten years for stepfamilies to fully bond.
The changes from the “honeymoon” of dating to the reality of marriage and living together are many and disillusionment often sets in quickly. The challenges in blending new families include hierarchy between stepchildren, relationships with former spouses and the complex feelings of children. The biggest challenge, however, is how to parent children who are not your own. The simple solution is that stepparents play the “good cop” role with their stepchildren while the parent parents.
The differences created by the family restructuring include different rules, habits, discipline and resentment to new family members. Most parents do not plan the “blending” process before marriage and it is critical to discuss these issues before marriage. A successful blended family can take up to ten years to fully mature.
See also https://www.pecoslawgroup.com/2015/05/15/the-proper-role-of-stepparents-2/