Fall When You're Ready [Brantley Gilbert fan...
After her older brother Ethan was killed in action as a Marine, Vanessa lives with the guilt and regret of never getting closer. She goes through her senior year with her brother's best friend, Brantley, still overseas. After months of only communicating with him through letters, he's finally home and it's time for him to prove himself to Vanessa, and live up the expectations Ethan would've expected from him.
I'm aware Brantley isn't a Marine, but I've read a few other fanfics in which he was, and wanted to give it a shot at writing a fan fic of my own with that twist.