If a young step child tells the step-parent “I wish you were my mommy / daddy” what would be an appropriate response?

Is this really what the child wishes or is s/he just saying “I love you, thanks for being my step mom / dad?

How would you answer? I think an appropriate response is “you have a father / mother who loves you. But, I’m glad to be your stepfather / step mother.”

What are your thoughts?