Scott and Artie
Scott Mohr is a secret service agent and Artie's son.
When Artie was arrested for treason he was in a serious relationship with a girl, but he never learned she was pregnant with his son until years after he became a Warehouse agent so Scott grew up without a father. As far as Scott knew his father, Arthur Weisfelt, was arrested for treason and went to prison where he disappeared.
After Artie learned about Scott, he desperately wanted to meet him, but at the time only Regents were allowed to have a One, the one person in their life who is not connected to the Warehouse that they share their secrets with. However, Artie threatened to quit the Warehouse if he wasn't allowed to meet Scott so the Regents decided that from then on Warehouse agents were also permitted to have a One.
Scott isn't a Warehouse agent, but he has helped Artie snag artifacts before in the past. Artie visits him in San Diego and they often bond by going to ComiCon together.