Jeremy Fitzgerald is a night guard at Freddy Fazbear's Pizza (The 1987 re-opened one). He is (apparently) married to Tetra, but doesn't think about it much. He is a good friend of Mike Schmidt's, despite the age difference. His son, James, was murdered by Vincent, causing Jeremy to go insane and lose his job.
He is a witness of the infamous Bite of '87.
After surviving his five long nights, plus the extra one night, the Lost Souls took him to see the Puppet. Tetra and James were there, causing a happy reunion. However, he discovered that Vincent killed all the Lost Souls, including his brother-in-law and his (Jeremy's) son. Then he went head-hunting. Failed, came back, the rest is history.