Earlier this year, Lauria signed up to star as Ethan, a former soldier who becomes a subject of interest for the CIA when Michael (Jeffrey Donovan) takes a shine to him.
Nix has now revealed that Michael and Ethan have a history and used to know each other.
"[He's] someone Michael knew when he was in the Armed Forces and he is, in a lot of ways, a younger version of Michael," he told TV Line. "He broke Michael's marksmanship record.
"He has a problem related to his sister. And the intelligence services have been sniffing around his character, so he comes to Michael and Michael teaches him what it is to do things Michael's way."
Nix added that Ethan is much more gung ho than Michael, saying: "He really wants to just run in and kick ass. So we really got to answer in a fun way for us, 'Why doesn't Michael just run in with a gun and bonk people on the head or shoot them or whatever? What would it mean if he did? Like why does he do things this way and why is that a good idea?' And Michael really gets to mentor this guy."
Lauria has previously revealed that Ethan is "really, integrally involved in the case".
Burn Notice airs on Thursdays at 9/8c on USA.
Watch a clip from the next episode of Burn Notice below: