Sam Hanna is an NCIS agent assigned to the Special Projects Department in Los Angeles and a former Navy SEAL who is also G. Callen's partner.
During the operations chronicled in the Season 6 episodes, Legend Part 1 (episode) and Legend Part 2 (episode), Sam revealed that during his service with Navy SEALs he had dealings with the Kidon division of Mossad. While in the Navy Agent Hanna saw service in both Afghanistan and Iraq. As a member of OSP, Sam's current partner is Special Agent G. Callen.
Sam has mentioned having two children in a previous episode. It is unknown whether this rumor is true or not, but Callen, when questioned of the subject refused to answer.
However, in a Season 3 episode of NCIS Los Angeles, it was shown that Sam has a wife and a young daughter. He and Callen later head to Hawaii to stop a possible smallpox break and during their time there, they form new friendships with the Hawaii Five-0 team led by Danny Williams and it's also revealed that Sam has some history with fellow Navy SEAL, Steve McGarrett.
In Season 4, it was revealed that his wife is a CIA agent who he worked eight years ago and that her real name is Michelle with Quinn being her cover-name.