more cockatiels?

Hi everyone I just bought my first cockatiel today. He's grey with white spots so I think he's a pied. I don't even know if he, is a he. His name is Bekham....Anywho, I've had cockatiels when I was a kid... but now my question to everyone is.... maybe in the future I would like to get more cockatiels.... how would I go about possible aggression, breeding??? Or should I just keep them all in separate cages? Cuz honestly I don't want them to breed.. bekham is now my babyboy and I don't want him to think when I get the others that they're taking his place. I don't want him to be territorial..... maybe some suggestions??????
Or should I just stick with him for the next 25 years????? lmao