What is the meaning of Sibling-in-law?

A relative of one's generation, separated by one degree of marriage:

  1. The sibling of one's spouse.
  2. The spouse of one's sibling.

The sibling of one's spouse.

The spouse of one's sibling.

Co-sibling-in-law: A relative of one's generation, separated by two degrees of marriage:

  1. The spouse of the sibling of one's spouse.
  2. The sibling of the spouse of one's sibling.

The spouse of the sibling of one's spouse.

The sibling of the spouse of one's sibling.

Source: wiktionary.org