Introducing a baby parakeet to a older one?

Wow, interesting question. So much to consider. Bad timing, I will say. You did not say how long you would be gone. It is not a bad thing to buy another bird, but if you are not going to be there to hand train it yourself, or give it the comfort it needs, it may be harder for it to adjust while being alone in a cage.. Depending on how long your vacation is, it could be even more stressful for a very young parakeet. A young un-handled baby bird will be uneasy in a new environment and will need a LOT of attention and "reassurance". Hand training is vital at this young age. You may want to consider a slightly older adolescent as a new companion. This bird would be adjusted and more independent. It can do it's own thing and has already discovered itself. You mentioned some doubts about your sisters being attentive to the birds. Does this really concern you? Are you sure your sister can handle this to your expectations? Does she have experience with feeding or caring for Boo? If so, she can feed and water the other fine. I'm sure she is quite capable of taking care of your little friends. You need to remember, though, that the new one is being taken away from "its" comfort zone too. Even if older, it will need a LOT of special attention also. You can not be guaranteed that the two birds will get along right away, or who will be the dominant bird until acclimation. That would be up to them. The older one may find the younger one more of a bother rather than a new cage mate at first. There will be big difference in ages. That's why I suggest a slightly older bird, (four months or more). At least it can take care of itself better than a baby. I would say wait till you get home before you purchase a new one, but this is totally up to you. I am not a bird psychologist, so I'm not sure I can give you a good answer either way. Only you know your Boo bird. If he is fine without his mate and continues to eat and talk and be social with you or your sister, I don't see a problem with waiting. As long as your sister is willing to be attentive with him he should be fine. If you do get one, I don't see a problem with keeping them semi close by. A reputable shop will not knowingly sell you a sick bird, but acclimation can be tough in any new environment none the less. Make sure your choice is of one that sits tall and is not puffy or eyes closed when you stare at it. Another good choice is one that is munching on food and not getting picked on (or is picking on others). If it is hanging around the ground, I don't recommend it. If it is sitting in the middle of a group, this is also a good sign. It sometimes is better if you take some time to watch the group and pick the one that has the best personality with others. A quarantine is not bad advice, but you don't need them to be toooooooo far away from each other. They both need companionship and seeing each other will make them perkier. Only you can make this decision. We are not there to assess Boo's psyche for you. Others on this site may have better ideas. We are all here to help you. Also, please have a vet chosen to help your sister in case of an emergency. You should always be prepared for anything. I will let you decide what you want to do. Either way should be fine. I hope this will help you. Have a nice vacation! Kisses for Boo!!!!! P.S. Every one may have a different opinion or advice to give you. It does not mean any of us are really wrong, despite a negative or biased rating. We are only giving you answers from our experiences. You have to make your own decisions. Common sense is the key, not a rating. There are a lot of great people on this site who I admire!.................UPDATE: Jolly Good!