Unless there's two of them, I know exactly the fic you're looking for! It's Refuge, by ebbj9891, part of her In Quest of Something series, and man is that fic amazing and soul destroying. Brian and Justin have been together for like 15 years or something (they might even be married at this point on the timeline, they get married on Brian's 40th) and Brian finally opens up about to Justin about being abused as a kid.

Anyway, here's the link http://archiveofourown.org/works/2352215/chapters/5189681