Kieran is a lowRed from the mining colony of Lykos. He is the older brother of Darrow by three years. He's considered the more sensitive of the two as he "bawled like a little girl" when their father died. As part of Darrow's mining crew, he's also very cautious, unlike Darrow. He and his wife have a son and daughter that are twins and are three-years-old at the beginning of Red Rising.
In Golden Son, it is revealed that his wife died shortly after Darrow had gone. He is now married to Dio, and they are expecting a child.
In Iron Gold, Kieran works for Darrow, alongside his eldest daughter from his first marriage, Rhonna.