How often can a child look nothing like the parents but it's still their bio child?

It happened to my a family friend. They're married and had their first baby a couple years ago. The baby girl looks nothing like them.

They both decided to get tested to see if there is a chance they were handed the wrong baby. It was positive for both tests, they are the bio parents. How often does that happen? The baby looks nothing like the parents but they are indeed the bio parents.

How often can a child look nothing like the parents but it's still their bio child?
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