He's the breadwinner in the residence, and they've been around for a few months before dear ol' Teacher decided to be a Vtuber, so I guess he had the time to get himself acclimated.
It's not like it was a decision that was made after just one encounter. And the princes are smart blokes. And considerate to a fault. I highly doubt that they would pull off that kind of stunt without considering the girls' feelings.