Okay, so what bird do you have right now? Do you have any bird right now in your home? You lost me after you gave the first one up for some reason, I couldn't understand what you meant when you said that you "took the first bird back to the breeder to show her the problem and she gave you another Conure"...I don't know what the problem with the first Conure was, he looked perfectly fine, his cere was fine...So now the second Conure bit your brother, and now you've given that one back too? Is that right? Or do you still have it? If you're not planning on keeping it then I'd give it back immediately, it's not fair to the bird or the breeder...
I think you need to stop at the moment and not bring back ANY BIRD from the breeder when you return this second Conure...I think you rushed into this decision, as we told you in the beginning of your post. And I think you know why we told you this now...It doesn't seem that you're quite ready for any bird at all yet...The cage that you have is way, way, way too small for either a Cockatiel or a Conure, and that will need to be remedied before you bring any other bird home...
Besides the cage issue, please do not think that bringing a Cockatiel or a Budgie home is going to solve your problems, as it just seems that you are not prepared for having a pet bird right now, neither emotionally or in routine/schedule...2 hours a day out-of-cage-time is not long enough for ANY species of bird, you must have at least 4-5 hours each day for the bird to be out of it's cage, regardless of species, otherwise you're going to end-up with a hand-raised bird that becomes nippy, as well as a bored bird that either screams all day long, or starts plucking itself, or both...
And believe me, as a long-time Budgie (English and American) and Cockatiel breeder and owner, they can both bite every bit as hard as a Green Cheek, even a small Budgie can break the skin if they want to, and a Cockatiel is no different in this respect than the Green Cheek...you're going to get bitten, that's just a part of owning a bird. It doesn't mean that anything is wrong with the bird, nor does it mean that the bird is "mean" or "not tame", it means that it's trying to tell you that something you are doing is something that it doesn't like. There's a learning-curve here, and you aren't going to find any bird that doesn't let you know when you're doing something it doesn't like.
It's never the bird's fault, it's always the human's fault...This is something that you need to remember...
You need to decide what exactly it is that you're looking for in a pet bird BEFORE you bring another one home...A Cockatiel has a completely different personality than a Green Cheek Conure does, they tend to be a bit more independent than Conures are, they aren't as cuddly or clingy, they will hang-out with you, but in-general a Conure is more of a person's "baby" than a Cockatiel is...HOWEVER, each bird is an individual, just like people are, so you cannot expect that you're going to get a certain type of personality, no matter what species you bring home...You must be ready for anything, you must be prepared, and you must have enough time for any bird you get...
Just make sure the cockatiel gets anywhere from 1/2" to 5/8" bar spacing and AT LEAST a cage size of 24" L 18" W 24" H. I found a very large, sturdy, and cheap cage off of amazon, and the bar spacing works for budgies up to senegals. Here's the link: https://www.amazon.com/dp/B00BLQDBD...olid=1U2UV8MALVIQY&psc=0&ref_=lv_ov_lig_dp_it
