Are Children Really Treated Differently?

Are Children Really Treated Differently?
What happens when there's a second marriage between 2 people, both having been married before with children from their previous
marriages? Kinda like the Brady Bunch! Parents and children have both commented to me that there is the tendency to treat your biological kids one way and your stepkids another. It can go either way, too.
Meaning, sometimes expectations are higher for your biological children; or, praise and consequences are different for your stepchildren. Obviously, the best way is to be consistent all the way around, but that's not always practical or realistic. Tell me your experiences. Let's get a dialogue going.
Dr. Rick