Paired kidney donors are a pair of people who want to donate their kidney to a family member or friend, but are not a good match. For example, if patient A is not a good match to donor B, but is a good match to an unrelated patient C. At the same time, patient C’s donor D is a good match to patient A. In such a case, donor D will donate a kidney to patient A and donor B will donate a kidney to patient C. Thus, both patients get a kidney from unrelated donors.