Hi Fiona,
Yes, same sex cockatiels can get along just fine. However, not all birds will get along. Most likely if you can find another older male that is lonely, they will get along. But you need to be prepared in case they do not get along. You could end up with two single older males. If you get another one, put the cages side by side so they can get used to each other. If they start sitting near each other and vocalizing to each other, this is a good sign. Once you introduce them, watch them carefully for any signs of fighting. You should have two separate food and water stations so one bird can’t prevent the other from eating. With any luck, they will like each other can share a cage.
Thank you for asking Lafeber,
Brenda