An interesting article looking at the role and rules for step parents and blended families.
If their role in the beginning is for them to just be a 'friend' to their stepchildren and not be too involved in day-to-day parenting, then it wouldn't be appropriate for them to discipline the children. However, if the adults have agreed that the step parent should take on a full parenting role, then it’s up to the two of them to define the rules in their own home and family.
http://parentinfo.org/article/the-new-blended-family-parenting-rules
