I've seen others post on here looking, so hoping it's OK (can't find a ficfinder for F&F?)... It's Dom/Brian. Dom's looking for Brian, finds him on his family's ranch and it starts out with Brian in a horse race, then walking back to the ranch. Brian has an older gay brother in a relationship, too. Thanks for any help!
Found: "Judas Kiss" by Joe Lawson:
http://assignations.org/joelawson/(thank you!)