Hi, I am looking for an RC novel. I forgot the name. Heroine's sister will work for an old doctor. Heroine's sister will die. Hero and heroine will spend a night together and then the old doctor will keep them apart marrying the heroine himself. After his death heroine will go as governess and hero will be a friend of the family. He will find out he has a son and they reunite.

Can someone tell me the name of this novel. I think its an RC one. Its been more than 10 years since I read it