I have a friend named Brendan. The Boy works with a different Brendan. Curiously, the two Brendans are kind of similar-looking.
One might point out that these Brendans are both Irish and surmise that their colouring and general facial structure comes from their heritage.
I choose to believe that every Brendan on the planet shares one or two physical traits with the next. These Brendans would of course occupy the full spectrum of heights, races, and builds; the first Brendan would look nothing like the last, but he would look kinda-sorta like the second one, who would look kinda-sorta like the third one, etc., etc., until we'd run the entire gamut of human variation.
A continuum of Brendans. A Brendinuum!
I mean, it's just so obvious.