Can you put other cockatiels in with other cockatiels?

yes you can. cockatiels enjoy human company as well as cockatiels or other birds company as well as the voice of other birds, just make sure that the cage you keep them in is big enough and doesn't crowd them--------------------------------------------------each cockatiel is different and males / females react different. try putting the cages close to first see if one gets aggressive. i had times where they would attack each other badly due to territory dominance.