Hi,
If he is a tame bird that you handle, then you and anyone who handles him is a companion for him. While he might chirp back and forth with a budgie, he’s not really going to view it as a companion. If he is mostly kept in his cage with no human contact, then he might accept a cockatiel as a companion. But then, he might not. Birds do not automatically get along. And since he has been a single bird for such a long time, he might not want to share his cage, toys & food with another bird. If you got another cockatiel, you would need to find another older bird. At his age, he is considered a senior – he would not appreciate a younger bird. While they are capable of living into their 30’s, most cockatiel live up to 15 years, so you can’t assume he has another 15 years. It depends on genetics and the care he has had. As long as he is happy, I would probably not change things.
Thank you for asking Lafeber,
Brenda