[mortenjorck]

Only if Backbone is a knockoff of Ember.

A better comparison would be to say that they both fall into the same typographic category; they are both humanist sans families with a bit of geometric rigidity; both have been compared to the classic DIN type.

That overlay isn't particularly useful; it only shows that the two families have comparable metrics and tend to follow the letterform patterns common to the category. A better visualization would be a closeup overlay of some characteristic letters, or a pangram set in each.