An Alphan was the designation given to any Peliar Zel native who lived on the Alpha moon of Peliar Zel. Throughout their history, Alphans have been in discord with the Betans and live in a state of perpetual tension with their neighbors.
In two separate instances thirty years apart, Alphan Kalin Trose represented his people in negotiations with Beta moon. The first, in 2337 saw negotiations mediated by Odan between Trose and the aunt of Lathal Bine. Bine himself would represent Beta moon in the second negotiations which resulted in a settlement. (TNG: "The Host")