I Didn't Mean to Say I Do, but I Do. I Do.
Years before joining the 118, Buck’s travels take him to El Paso, where he meets Christopher. When Eddie comes back from Afghanistan and Shannon leaves, Buck ends up staying. As bills pile up, the best move is for them to get married, just for convenience, they’ll divorce when Eddie comes back from his re-enlistment.
Then Eddie gets injured and it’s just easier to stay married for a little longer, while Buck gets started at the 118. However, Buck doesn’t mention his ‘husband’ and kid, not feeling like they’re his to keep. When Eddie gets the offer from Bobby, they decide to lie and pretend they don’t know each other, so they can work together.
The whole lie gets out of hand as feelings start to become real, until it all comes to a head in the aftermath of the fire engine explosion.
AKA: Secret marriage of convenience buddie slow burn AU, where Buck and Eddie have been married for years so Buck could adopt Chris and no one at the 118 knows.