Yes, I have had Howard since he was weaned. While he has always been an only bird, he has two canine siblings, a borzoi and a whippet who he enjoys ordering around and who he is not the least bit afraid of. Howard is cautiously curious about both dogs and people. But the one time I took him on a play date with another AG a few years ago it was a disaster: he started to cry and waddled back to me as fast as he could repeatedly. That was the only other contact he has had with a parrot since he was a baby.
Trying to arrange a few visits is hard, as the other bird is a few hundred miles away. But you are right again, the current owner is a friend of a friend. Because I work a lot and sometimes travel, Howard is often alone, and my friend thought that his life might be enriched by having a constant companion. Howard is very attached to me - in fact, he is sitting on my shoulder preening as I write this - and I suspect would be very protective of his quality time with me and hence jealous of an interloper. But if - and it is an if - the two birds really got along, maybe it would be good for both. On the other hand, I do see your point about the other parrot being traumatized if rejected.
Thank you for the thoughtful responses. I will try to post a couple of pictures of Howard and respond to other posts over the weekend.