as a child with a step-parent since i was a small child, no-one here unless a step child themselves, can in any circumstance understand what being a step child is like. it is great 90% of the time, but 10% is unimaginable. a stepfather is very different then having a stepmother. fathers create their loving bond through interaction with their children. so technically a stepfather can act no different then a regular father. a stepmother cannot, as her bond with her natural children can never be mimicked (it can come close, as it comes from carrying the baby from the womb. a stepchild to a stepmother feels no close motherly bond their entire life, and this can cause undue anguish.
people have mentioned here that it will fall under the category of respecting elders. that is a huge difference. respecting ones elders and ones parents have much different rules. if a parent tell you do get him/her something, you have to. if an older person does, you can decline if you have something else pressing to do. a parent makes that pressing matter go to the back burner.
i think the poster meant respect in the meaning of reverence. and the answer is no. at least medioraysoh. mederabonon, it is learned from the extra es in kabed es avicha c”ES” emecha, that all other wives of a father. (this goes back to the day of multiple wives). a step father may not have even this.
but before everyone jumps down the posters throat, just thank g-d you have both your parents. while seeing your natural parent taken care of does allow for some comfort in what you go through during your life as a stepchild, it doesn’t compare to the hurt of not having your mother or father there in your life.