I would imagine so. I have two cousins (from two different aunts) who are mixed race, and people are often confused as to how I have "black" cousins.
The mother's response to her niece at the close of the article is perfect, "All I could think of was 'It's the difference between fluffernutter, peanut butter and Nutella. All different flavors, but all tasty'." It would be great if the general public could accept that as well. Not really sure why society is so afraid of "different."
A simple, "No" would answer the question and shut the questionner up (hopefully). Depending on how aggressive and nosy the questioner is, your friend might consider these variations.
Is he adopted? No. Are you? Why would you ask such a stupid question? And that would be your business because.....? You're kidding, right? He's the spitting image of his mom. No. We bought him at a yard sale. No. He was genetically engineered. No. He's American. Yes. He was the pick of the litter!
That's sad. I don't like to think that so many people are closed-minded these days. Of course, to give that person the benefit of the doubt, it might have just been a careless attempt to make or extend conversation.
It's sad that a family of various backgrounds is not acceptable to some people. Growing up in a non-native home brought difficulties for me, siblings and parents. I would think they themselves are a minority tho, don't you? ones that find mixed families..unacceptable, that is