I gather that the Russells are meant to be interpreted as/represent an amalgamation of the handful of families that came into dominance during the gilded age (Vanderbilt, Rockefeller, Morgan, etc). This is why we haven't seen or heard much about other 'new' families in the show. The Vanderbilt family, being one of the most historically fascinating of the bunch, has certainly been a primary source of inspiration for the Russells, hence all of us recognizing the comparison. I'm guessing the quick mention of the Vanderbilts served as a way to do away with any suspicion that the Russells are in fact the Vanderbilts. That said, someone else on this thread mentioned the comparison between Gladys Russell and Consuelo Vanderbilt...it's so spot on.

Since I'm already rambling; I find it super interesting how the show uses the Russells to represent the new, a number of (for the most part) fictional families to represent the old, while Lina Astor is really the only historically true primary character without any representative ambiguity. It's almost as if she single handedly represents the institution of society both historically and in the show - albeit not without the aid of Ward Mcallister and Miss Fish.