Joe Faxon was an ambassador assigned to negotiate with the Aschen.
After Faxon was assigned to the SGC, he took an instant liking to Samantha Carter, even asking her out to dinner. When he and Major Carter discovered that the Aschen intended to destroy Earth now that they knew about their sterilizing population through an anti-aging vaccine, he told her to leave him behind so that she could make sure the SGC closed the iris protecting their Stargate.
In an alternate reality where Earth was a devoted ally of the Aschen, Joe Faxon and Samantha Carter were married. When they were having trouble consieving a child, Samantha discovered that the Aschen had managed to sterilze over ninety percent of Earth's population.
When she revealed this information to Joe, he admitted that the numbers were only supposed to be a third of what they actually were. Joe had known about the sterilization, which was termed 'limiting growth.'
Samantha managed to convince him to obtain a GDO for her and the rest of SG-1, but only agreed to give it up if Samantha had no further part in what they were planning. He would not let Jack O'Neill "endanger Sam's life."
Despite this, however, Samantha threw herself into the plan once more and Joe Faxon was forced to watch his wife die in the attempt to send a message back through time to prevent Earth's alliance with the Aschen. (SG1: "2010")