Born of a Concubine

I really like this book; I've read it several times.

The author's biggest flaw is that he can't distinguish between his cousin and his maternal cousin, always calling his cousin "brother" and "cousin."

The terms of address are all over the place—one minute it's "cousin," the next it's "brother cousin," then "sister cousin," then "sister cousin," and so on. Why is a younger sister-in-law called "sister-in-law"? If it's an older sister-in-law, she should be called "sister-in-law."

It means the milk came in so quickly, there's no need for lactation stimulation?