Pegasus

Everyone knows pegasus are winged horses right? WRONG! Pegasus used to be ONE horse, so why are there so many now? Even if Pegasus did breed with a normal mare, and the foal had wings they would be useless and only have stubby things sticking out of it’s back. What I would like to know is how the BREED pegasus came to exist! There is only THE Pegasus who, originally, came from Olympus. Who can end my confusion and my one question, why is there suddenly a whole breed of pegasus when there used to be one??