Thanks, K.E. The thing about individuals with mixed ethnic backgrounds is that it's turned out to be even more extremely unlikely to find a stranger who is a good donor match than it is when the patient has a homogeneous ethnic background. Even with blood, the easiest thing to transplant successfully, it turns out that matching A, B, AB, or O also requires taking the rH (+ or -) into account. Sometimes individuals can have rare serological factors that can complicate a transfusion. If a patient is scheduled for a surgery where blood transfusion might be required, patients are often encouraged to bank their own blood for the procedure.

For organs, there are many more factors. You might find this article useful:

sbs.com.au/news/article…