If Youtarou had taken up Minori's invitation to sleep with her, I bet Kaho would have been willing to cover for him with the parents (at least in my twisted fantasies, that's what would happen).
@Markgraf I think he has already slept with her...not sex...just sleeping. I think his dad actually wants him to have sex with her and marry her. I think his mom is trying to set him up with Saionji. There can't be any other reason parents would send the teen daughters of their employers to live with their son.
As for the girls' parents, I think they are fine with their daughters getting close to him too. Minori's dad probably knows she loves Youtarou, he probably even told Kaho to set them up.