Responses
During that time most nobles' marriages were political and it's extremely rare for them to be in love with each other. As long as the wife has borne an heir for the family she can discreetly keep a cicisbeo (a typically younger male lover/escort), just like the husband keeps a mistress. Since Olivier is young, unattached, and attractive, it's not surprising for him to have affairs with married women.
Of course, this is all strange and inappropriate in Charlotte's (and our) eyes because commoners marry for love for frequently than nobles.
While I like this manga I just hate the ML and his clients like seriously ? Are you obligated To sleep with your clients and married ones on top of that ?! Ugh disgusting (︶︿︶)=凸