@mismarca
i think there was never a noble who became a mistress to another noble sometime it happen if he is king but it's 1% kinda thing and they usually drive the first wife by framing her for doing something "bad"
but since the first wife is a princess and the other mistress is a high ranked noble it won't be logical unless he has the rank of king and since silk is an only child she must convert her husband to be part of her family to inherit her father but since she'll be a mistress her children are illegitimate and therefore are not worthy
on the other hand princess when marrying a man of lower rank show a very great obsession with him and turn into a very blood thirsty yandere that eliminate any love interest for her husband on some worst cases from certain countries they tell on him to their father or brother and decide to frame him and execute him
overall this harem have the worst chemistry possible thou the two maid could work out since many noble did have an affair with their maids with no extreme consequences