"You won't understand until you have your own kids." "You're not the parent here." "You'll never love them as much as I do." "Only a real parent would understand." "You're not their real dad." Have you made these statements, or statements, such as these to your new spouse concerning their new role as a step parent? If so, stop.
Although your intentions may not be malicious, statements such as these are often terribly offensive to step parents. True, your new spouse may not be your son or daughter's biological parent. But, it is important to realize that as your spouse, your new spouse values the relationship that he or she has with you and also values the relationship they have with your children. In fact, many step parents make it a priority to ensure that their step- son or step-daughter are comfortable and accepting of their presence, and seek to play an integral role in the lives of their step children. With that being said, imagine the hurt that could be inflicted on a step parent by the utterance of just one of the quoted statements above.
If you are having trouble communicating with your new spouse regarding the expectations you have for them in their role as a step parent, seek family counseling. Often, family therapists are able to give spouse, and even children, guidance and advice on how to handle the conflicts most commonly experienced by blended family.