Short answer ... yes, it is possible to have more than one parrots and they still learn to talk. It is just less common.
The longer answer is that parrots will naturally mimic sounds in their environment. Especially sounds they enjoy and find interesting or useful or sounds that are repeated often. If you have a close bond with your bird, what you do and what you say will be very important to your bird and he is more likely to want to mimic you. In contrast, if your bird has a special bird friend or lots of bird friends, your sounds are probably going to be lower priority than the sounds made by other birds. You are still part of his environment and he might pick up on something you say or do often ... but it less likely to happen.
Tendency to mimic varies a lot between parrot species and even between two birds in the same species. There is no guarantee that a particular bird will show interest in mimicry, even if they have the potential.
If you do hear your bird "talking", you can reward him with praise or treats to encourage more mimicry. Simple greetings like "hello" are some of the easiest to pick up because it is easy to get into a habit of greeting your bird each time you visit their cage. Consistancy, repetition, and praise are key aspects of successful training.