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It is what it is. Photography is capturing the reflection of light. Darker skin reflects light considerably differently than lighter skin. Put the two of them together, and you get some lighting challenges. I sometimes shoot biracial couples' weddings, so I occasionally get to deal with this fun challenge.
The way I've handled it -- and it's certainly not the only way, or necessarily the best way -- is to expose for the lighter skin. I prefer not to have blown highlights. I can always edit back in the darker skin. It's not much, but I hope it helps some.