One thing that few people understand about blending families is that they are not made in a blender, they are made in a slow cooker...it takes time to blend a family and each person has his or her own pace. Forcing relationships tends to make people dig in their heels instead.
This is even more important as far as discipline is concerned. The older a child is, the longer time span before a step-parent, or "bonus-parent" as I like to refer to them, should begin disciplining him or her. Too soon and the child will show animosity toward the step-parent. Easing into disciplinary changes is easier for children. It allows them to build trust and rapport first.
Mary Bowles, PsyD, abd, LMFT