Can cockatiel and a budgie in the same cage?

Each and every bird is unique and some are more violent than others. Introduce them a couple of times first and monitor their behavior together. If either of them show aggression, separate them immediately, and do not allow them to live together. If they get along or tolerate each other after a few weeks, then thy can be allowed to live together with continued monitoring to make sure they don't turn on each other when forced to share space. If the baby in question is a chick, then it must live in an incubator or in a nest box with a pair of attentive parents until it is old enough to live in a cage. Some birds will play foster, but some will not, so don't count on it.