The Speedster and the Archer
When Barry was very young, his mother was murdered by some strange force and his father was ripped from his grip, crying out to Barry, telling the small eight year old boy to remain strong. Even though they gave the man back to his son, Barry could never un-see what had happened to his mother. Ever since that day, Barry believed in the impossible, no matter what other people told him.
Belle!Barry meets Beast!Oliver and they fall in love.
I may miss a few details.