It depends on how far your brother wants to drive, but within a 10 or 15 mile radius of Buffalo Grove, you can find just about any food form you can imagine -- not just in restaurants, but also in fabulous ethnic grocery stores.
For example, within 1 block of Chaihanna, you have two great Russian delis/grocers and America's Market, where you can get specialty items from all over the US.
In Wheeling, just east of BG on Dundee Rd (Chaihanna is at the corner of Dundee and Buffalo Grove Road, hence the focus on places on Dundee Rd), you've got Carniceria Jimenez, which is a large Hispanic grocery store with a nice café serving very good food, Krystyna's Grocery and Deli, which specializes in Eastern European foods and has a lot of ready-made carry out items, and, back to the restaurant category, on 83, just off Dundee, there's Pita Inn, an absolutely great place for cheap Middle Eastern food.
And west on Dundee, you have Le Titi de Paris, should he crave French food.
http://www.letitideparis.com/ -- there is a thread on Le Titi, plus their website offers info on wine dinners, classes (even for kids, lunch bargains, and various other offerings of this nice French spot.
Once your brother knows the names of suburbs, he can search this site for recommendations, too, because there have been a lot of threads on where to shop and eat, either by suburb or by food category. Korean, Spanish Tapas, Chinese, Mexican, Indian, Japanese, and a host of others are are within 1/2 an hour drive of any point in Buffalo Grove.
And tell him "welcome to the area" for us. We look forward to inviting him to the community (and welcome to you, as well, since this is your first post).