Your brother's wife's cousins are not related to you and the English language has no special term for that. The same applies to the cousins of a stepbrother's wife.
A hoe.
Derek Huff (Adam Scott)'s wife Alice is portrayed by American actress Kathryn Hahn in the 2008 film Step Brothers.
aunt
We call "Mami" to moms brother's wife.
probably by her name
sister in law
If you are close to your step-brother, or to his wife, you can call her your sister-in-law. If you are not close, you can call her your "step-brother's wife."
In a marriage in which both the husband and the wife have children from a previous marriage, the children are step-children to the parent who is not their bioloigical parent, and are step-siblings (step-brothers and step-sisters) to each other.
Brother-in-law
Pick up the phone
Sister In law
errrr, no maybe nephew