Keeler is the lead navigator aboard the Sleipnir, a battleship from Earth. It's been revealed that Keeler's genetic modifications are flawed, which caused him to develop an unspecified condition as a teenager. His medical assessment records were falsified so he would be eligible to join the Alliance. This condition threatens to interfere with his ability to perform. It is suspected that Keeler is in on the Shady Plan.
Keeler and Encke have been assigned together for about six months.
He is most likely named after James Edward Keeler, an American astronomer discovered the Encke gap in Saturn's rings. The Keeler gap in Saturn's rings was named in his honor.
It's mentioned that he is highly trained.
Keeler has acquired a sort of illness that makes him exhausted,faint. In chapter four it has been proven that he had this illness since birth and was on bedrest in his youth,he managed to bribe superiors to disregard his medical history. Also in chapter four it has been made clear that Encke knows about this condition since they were assigned to each other.
Keeler's past besides his illness is vague, once again in chapter four Keeler does not unpack anything.
He seems to have a "more than friends but not lovers yet" relationship with his fighter, Encke.