Great-Grandson's Wife

What kind of wife is the most difficult to be? Not an evil mother-in-law, a mistress of N little wives. It's not like my husband doesn't care for me or my parents don't love me. But... My husband had calculated this, and he had to swear a poisonous oath as a stepping stone to get married. Even if my mother-in-law knows her little thoughts, she still has to pretend not to know. The Qin family, where four generations live together, welcomed a fourth-generation bride...