What do Bob, Jack, Hughie, Jims and Patsy all have in common in the novel, The Thorn Birds?

Bob, Jack, Hughie, Jims and Patsy are the surviving Cleary brothers, collectively known to Justine and Dane as the Uncles, or Unks for short. They are all short men with red hair, who grow to resemble one another in personality, as working Drogheda becomes their life focus.