My fiance and I both love calling eachother "Mommy" and "Daddy" during foreplay and sex, we also enjoy "slut" and "whore" and "princess" for me and "good boy" for him, and saying things to remind the other of our dominance like "I own you", "you're mine", "you belong to me" and "you're my bitch" and we make the submissive one say it.
It is in noooo way an incest/pedophila fetish, it is purely out of a love for submission and domination. But we both enjoy being dominant so we take turns being each others bitch. Outside of the bedroom, we are perfectly respectful of each other, it is in no way an abusive relationship, I am absolutely in love with him and he treats me like his princess and we trust each other 100%.
We both enjoy a little bit of pain during pleasure, so I give him what he likes while he screams my name and "mommy" along with other things along the lines of "yes mommy" and "please mommy", "you own me", "I belong to you" and ending with a "thank you mommy" when I make him cum.
and he does the same for me, and I give him a "thank you daddy" in return.
as one of those "weirdos" who enjoys to do this in bed, I can assure you that some of us do it out of an interest in dom/sub, and is in no way an interest in incest and pedophilia.