No, I don't think they count according to the OP. These adopted children of American celebrities are all U.S. citizens and live in the U.S. (at least some of the time). So even though they are foreign born, they aren't currently "foreign".

This is correct. I was looking for people for whom they're primary legal tie is to somewhere else other than the United States. On the flip side if the Daughter of the German Ambassador to the US was really famous, I'd count them in this search.

I didn't even know Madonna has children, and I couldn't tell you the names of any of Brad and Angelina's kids. I doubt I'm alone about either. I just can't see these kids as the "non-American under 18 best known to Americans."

Especially since as others have said, despite where they were born they're all Americans.

The only child "celebrity" I can even think of is that Ashleigh, who won Britain's Got Talent with her dog, Pudsy. But then, I know a lot of dog lovers.

This is the first round.