Interestingly enough, the sister-in-law in The Miniaturist acts as the requisite mean stepmother. She wears black, forbids sugar, and excesses of any kind, yet she harbors a dark secret.
Nella has been invited into a sumptuous world--the house of a wealthy Dutch tradesman. In exchange, though, she must keep the family's secrets, something which makes Nella uncomfortable.
Johannes has freed the slave Otto and educated him. There is good in Johannes, yet he has married Nella under false pretenses.
Nella is childlike and powerless in the marriage which explains why she is drawn to the miniaturist's guidance and mesmerizing control.