Was Ruldolph one of original reindeers?

No, Rudolph is a fictional reindeer created by Robert L. May in a 1939 story for Montgomery Ward. This makes Rudolph one of the more recent additions to the reindeer team, as Santa Claus is traditionally said to have eight reindeer: Dasher, Dancer, Prancer, Vixen, Comet, Cupid, Donder and Blitzen.