I know this is an old thread, but to be honest...to me personally it doesn’t sound like they are off or trying to sexualize you. They sound like they are comfortable in their sexuality and their bodies. This is not to say your feelings are unfounded....they sound like they do not realize they extent of which it bothers you, and they just see themselves as “hip, free” parents. Like the “cool” parents, you know?
Again, being an old post...have you had a heart to heart with them about this and your feelings? I know you said they make comments on you being prude and joke about their sexual activity, but maybe a really deep heart to heart could help. My honest opinion, based only on this post of course, is that they really aren’t being deviant or malicious....I think they just see themselves as a fun, sexy couple. I’m sorry you have to deal with this as it makes you feel unsettled.
Honestly, I know some parents exactly like this. Not mine, but they do exist.