Shon was orphaned as a young boy when his parents were killed by the Cardassians. He grew up with his new, adopted, parents on Fellowship Colony along the Federation-Cardassian border in the Demilitarized Zone. During his time on Fellowship, he forgot much of the Bajoran language that had been taught to him by his natural parents. After the Federation ceded Fellowship and numerous other worlds to the Cardassian Union in the Federation-Cardassian Treaty of 2370, the now teenage Shon joined the Maquis after the Cardassians killed his adopted parents.
After Ro Laren assumed command of the Orb to evacuate refugees from Galion to Bajor, she asked first officer Sharfer if any other Bajorans were assigned to the ship. Shon was the only other Bajoran on board, so Ro had him promoted to the bridge and he was to be on duty whenever Ro wasn't so if the ship was stopped by a Dominion-Cardassian patrol, they could keep up the pretense that the Orb carried a Bajoran trade delegation en route back to Bajor. (TNG - The Dominion War novel: Behind Enemy Lines)