NP having “adult time” while I’m here

This is the second time that the parents of the baby I nanny are having sex while I’m there. While we have a super close, almost family, relationship, this seems beyond acceptable.

They even were having a conversation in front of me, trying to figure out when the last time they had sex. That alone was weird. I tried to break the awkwardness by laughing it off and saying “just let me know if I need to take the baby for an extra long walk.”

Edit: I’ve been with them for a year. I don’t plan on leaving. They’re friends as much as employers. Both my partner and I are close friends with them, and I’m considered an aunt to the baby

I have NO IDEA how to handle this…. Help 😳