None in my current flock were really planned... per say.
Casey was a gift to me as friends of the family knew I had birds, knew I loved birds, and she needed a home! Well, the friends of the family were friends with some cockatiel breeders, and she was being sold... so they bought her for me, although somehow, I think, I ended up paying for her.
The bourke parakeet came with a group of other keets from an elderly couple deciding travel across the country and couldn't find a bird sitter for them... so instead gave them up. They had belonged to one of my mothers coworkers parents. Out of the small group, she's the only one left.
Pistachio (and his family) was quite literally dropped off at my doorstep. I have actually known him for longer than I've had birds, as at the time, he had belonged to a neighborhood kid, and he and I were about the same age. As little boys grow up, they forget about their precious pets and discover girls and sports. He and his family were offered to me several times, but I figured I'd never see them because they were never brought over... so the day they were brought over, I had no advance warning they were arriving! I found homes for his two offspring, and sadly lost his mate earlier this year.
Tomi Girl was found by some "friends" and they decided to keep her... in a smoke filled home (practically everyone is a chain smoker and/or does drugs and drinks alcohol) over-run by sick cats. I did what I could for her, which wasn't much... that is, until they simply "forgot" to feed her (found this out later) and she was ~50% underweight. Took her home that night, which thankfully they said I could. I was going to take her even if they said no!
Faye was "payment" for watching over a house. I had previously gotten a male cockatiel from them after the female died... then received a screwed up young dog (I put all blame to this family! quite furious with them!) from them that later had to be put down. I hate that I wasn't able to do more for him... and then Faye's mate died (they blame mice... mice who would actively go inside the cage during the day! I blame them once again) and she was offered to me. They decided to keep her for a while longer, that is until they went out of town for a couple of weeks. I watched their house for them, then after a few weeks of them being back, and on December 25th, they decided to offer her as payment to me.
Charlie was offered to me because at the time I had owned a cherry headed conure. His foster parents wanted him to be in a safer home, his screaming was horrendous (imagine that! a house that included 2 macaws, 3 amazons, 3 green cheek conures and 2 rosellas... and he was the loudest!) and they offered him to me. I accepted, but as it turns out, he and Noel never really did get along.
All the cockatiels and bourke parakeet live together. However, only Casey and Charlie demand interaction. For the most part, the rest of the birds don't desire contact, and I'm not going to force them to interact with me if they are happy as is. If they want to interact with me, that's another thing - and I'd be more than happy to oblige them!