I'm so dumb :/

[The Unintelligible]

While it obviously doesn't automatically hold sexual implications, he could have effortlessly made that the case if he spent a night. An innocuous sleepover could turn into a wild orgy in mere seconds.

The only conditions that would really need to be met is him doing the seducing and enticing instead and their parents not to be home.

If it isn't initially their intention if he really wanted to he could have probably still made it happen.