For a brief while in my childhood I was a stepchild, though I never got any of the Cinderella-ish treatment sometimes associated with that word. I was lucky to have a great childhood and a great stepdad.
Fortunately I could see into the house through another window, and I watched how our good boy sat there patiently by the door the whole time, not jumping or even pacing. What a good boy.
Even if they do feel like stepchildren from time to time, they are quick to forgive and forget.