The Dairymaid’s Secret Desire by Maisy Borten
Although Elsa knows that Roderick, the lord's heir, is pursuing her only for her generous breasts, she can't help but respond to his bright eyes and broad shoulders. But it's not only her heart that's affected: the women of her family begin producing milk as soon as they become intimate with a man.
Elsa can guard against physical intimacy, but Roderick's very presence stimulates her inherited trait. Worse, she finds herself falling in love with the young lord, a man far above her station. As her master, he can use her ability to lactate for whatever purpose he chooses – unless she can somehow keep her ability secret.