Gibbs has been a Sentinel for a long time, even before he joined the Navy. His first wife, Shannon, while not a registered Guide was good enough for Gibbs to function. After the death of Shannon and Kelly, he went into a tailspin until he joined NCIS and Mike Franks helped him settle in. His senses went offline (i.e. back to normal human baseline), and he never used them again until he met Tony DiNozzo in Baltimore. Gibbs nearly zoned out the first time he got a whiff of Tony. The man didn’t even know he was a Guide. Once Tony joined NCIS, Gibbs dragged him to the Sentinel and Guide Center in DC where he was tested. Gibbs made Tony his Guide as soon as it was official and moved the younger man into his house. At first, Tony was uneasy, not only as a new Guide with a Sentinel, not only as a new NCIS member, but also with having a steady monogamous relationship. Tony had slept with other men and woman, but no matter how much he showered, Gibbs could still smell them. He came to a decision, with the help of Blair, and made the effort to be only with Gibbs. When asked by Ducky, Tony said he was tired of hurting his Sentinel. In the beginning, only Ducky and Abby knew about them being a Sentinel/Guide pairing, but once Gibbs was sure Kate and McGee were sticking around, they were also told. It made things slightly uncomfortable, but eventually everything settled down. With even more Sentinels being found in the Navy, Gibbs and Tony help them settle into a routine and make sure that the Navy superiors know what issues might come up with Sentinels and Guides.
