I'm not sure how common his results are, but I saw someone with Mexican heritage on "Finding Your Roots" on PBS who I think had a similar percentage of Middle Eastern DNA.

It was politician Linda Chavez, and in her case, they discovered she was descended from "conversos" - Jews and Muslims in Spain who converted to Catholicism under pressure from the restored Spanish kingdom, which had reconquered Spain from the Moors around 1500. It's a really fascinating history.

Chavez and the other guests on that episode had varied combinations of European, Native American, Middle Eastern and North African ancestry, the latter hinting at Moorish roots that BigAl suggested in his earlier post.

Also, about the percentages - although we all get 50% of our DNA from each parent, we don't get an even split of their ancestry - siblings might get varying amounts from each parent. I inherited 16% British & Irish, but my brother inherited 25%, for example (those results are from 23andMe - he hasn't tested yet at Ancestry).