If I recall, you've never had any birds as pets before, have you?
I will second not bringing home any other bird until you get that Golden Conure home and have had him and only him for at least a year, if not longer. There are many, many reasons why we are telling you this for your own good, but the main one is that you need to build a bond with the Golden Conure first, get him settled-in and used to your home, your routine, and just "you" in-general, and most-importantly you need to see what type of personality this Golden Conure is going to have, because it's not going to be anything like the way he's acting now in that pet shop or at the breeder or wherever you're getting him from...And I hate to bring this up, but he may very well have some neurological/psychological/behavioral issues going on due to his very late-weaning and other problems...But even if these issues didn't exist, you still need to form a relationship in your home with the first bird before you even think about bringing home a second bird.
Having more than one bird, particularly of different species, can be challenging at best, and you should NEVER bring two different young parrots of two different species home together or close to the same time, unless they were raised together. I put a good year and a half to two years between bringing any of mine home, simply because I wanted to bond with each one, I wanted to be their "flock" and their "person", and I didn't want any issues with that happening or interference with it happening, such as the two young birds bonding with each other and not me, OR more than likely what will happen with that combination that you're talking about bringing home is that they will not get along with each other AT ALL, and then during the time when you need to be spending as much time as possible with them to form a strong bond with them, instead your time will have to be equally split between two young, baby/juvenile birds that most likely will not be able to be out of their cages together at all. So instead of forming a close, solid relationship and bond with the Golden Conure first, before bringing in another young bird, you're not going to have the time to do so as you'll be split between the two, so you'll not ever form any close bond with either of them...
The other huge issue you're going to have is the issues with territoriality, with two new birds fighting to be dominant over their new home AND their new person, to the point that you're likely to end-up with two birds that can't be anywhere near each other, especially when puberty hits. As already mentioned, Caiques are not at all easy parrots to have as pets by themselves, let alone at the same time you are also bringing home a baby Conure...Caiques are very unique parrots with behaviors and personalities that are like no other parrot species, and they do not at all like to "share" with any non-Caiques at all. So again, you're going to end-up with two young, baby birds in their new home at the same time, fighting over the house, and fighting over you, and this is a recipe for disaster...
***There will be plenty of hand-raised, baby Caiques for you to bring home in the future. As a person who has never owned any larger species of parrot, or any parrot for that matter, not long-term anyway, please, you need to put your wants to the side, and start-out this very adult relationship and responsibility that you are taking-on by doing what is going to be best for that baby Golden Conure that you have been dealing with forever. Bring him home to his new house, and make yourself and your time ALL HIS, which is what he needs during his first year with you, and what you need if you want to be closely bonded with him...This can't be about what you want, it needs to be you doing what is best for the baby bird you have already committed yourself to. If you bring home two baby parrots at the same time, one being a Caique, you're going to find yourself in a situation where you can't spend nearly enough time with either bird, you're not going to form any type of close bond with either bird, and you're going to have two birds that can't even be in the same room together because they are so territorial about you and the home that they are extremely aggressive...Not only with each other, but also with you!!!
What I'm saying is you are jeopardizing your relationship with either bird by doing what you are thinking of doing.
