When you know a bird has been in a pet store a long time it really breaks our heart. I'm afraid this guy will just replace them with more.
[i felt the same for a Swift parakeet, another aviary bird, left for a year or more in a small cage at the pet store which was way better sounding than what you're saying - i haven't looked for him in a while as it is way too painful - it still hurts knowing what they're missing - at least these people were feeding the Swift well.]
Bourkes are a lot like Budgies but are usually kept as an aviary bird & need a lot of interaction to be tamed. The Bourke's was the Parrot that got me back into my passions of birds. Because they have larger eyes [they remind me a bit of a sparrow hawk] they see a lot better than Budgies. They get up early & go to bed later & are very active at dusk. They have a sweet whistle call.
Are these regular Bourkes? Photos never seem to do them justice.
Bourkes Parakeet - Birds 
- this is her own bird - the woman who wrote the artcle - as she wrote to me about Jerry when i asked her about their tameness & housing one in a cage.
- or Rosy Bourkes?
The Bourke’s Parakeet
A lot of people wouldn't know what they were looking at. The regular type are a very understated bird but i think they're very beautiful.
I hope all goes well - but maybe the local humane society should be alerted - he will buy more.
Breeding a brother & sister is not good unless you are a breeder & know their parentage - which may already be brother & sister!