I haven't had a big issue with it. Pogo was my bird and preferred me but loved my ex-h almost as much, if not the same. He snuggled better with him but would also snuggle with me. He would also go sit on visitors if I handed him to them. My mom came over often so he would sit on her lap and get drinks from her glass (which I discouraged). 
Darwin is so outgoing but when new people come over he clams right up and acts shy. But he's not shy with my bf. He is often on his shoulder. I think he prefers his shoulder as they are broader without all the hair in the way. But he prefers me, he is my little buddy.
Itsy loves me but prefers my bf. She seeks him out and will fly laps when he comes in the door. She has flown upstairs looking for him a couple of times. She will step up for him when I can't get her to. But she is still sweet with me and I can still do anything like do her nails, give meds, etc.
Tiki is nervous of everyone but me and her previous owners.
Quack usually prefers men but she is in hormonal mode right now and tries to feed me. She likes my bf but doesn't flirt with him like she has with other men she has seen. It's probably best as she can bite pretty hard and I wouldn't want my bf to be the one to have to deal with her as I don't think it would go well.
So I haven't really had to deal with the rejection that some people do when they lose their baby to someone else. Pogo was the only one I had from a baby and he probably would have switched allegiance if my ex-h and I had stayed together. But I don't think he would have hated me or rejected me as he already liked both of us a lot.
I do think socialization helps. Quack is kind of my shy bird but she loves having company and really performs for them! It used to be she would just be all excited after they left, like she wanted to talk about the fun visit but now she will whistle and dance and be crazy for visitors. 
Didn't have the time to get back straight away but I got more responses than I thought I would lol. Your birds all sound very cute and sweet
I think that some birds prefer guys because of less hair all over, I think it annoys em haha. A U2 I know will groom women's hair back out of the way if it's down.
How old are all of your birds? Aka, are they mature? And all African Grays? I think that the particular species sometimes, not always, has to do with how strongly they bond and how friendly/one-person they are. I've also heard of Grays being more independent in general. On the flip side, do you pick favorites?
A small tale about Sunshine Tiel, who came to us last April. The first few months (which included quarantine time) Sunshine was very attracted to my wife. He'd fly out of his cage and right to her. I was hoping he'd establish a strong bond with her, like Milton has with me and Titan had with Marty.
Late summer, he started to get much more interest in me. Nothing had changed in the household, except Sunshine was now integrated into the front room with the other birds. Sunshine began to actively seek me out, rather than Kathy. He didn't "turn" on her, just wouldn't stay with her for any time, he would begin to flock call, then actively try to seek me out.
It did disappoint me because I hoped Sunshine would've accepted Kathy as his "favorite"...now I have two birds (Sunshine & Milton) jockeying for my attention all day!
Hmm. Thank you for sharing, this is exactly the kind of thing I was looking for when I posted; personal experiences. By nothing changed, though, what do you mean? When Sunshine was still in quarantine who fed him/saw him/played with him often? And when he moved with the others, was it that you started doing more with him? Maybe he was following Milton's lead - young birds learn from other birds. Or maybe it was that you were newer to him and thus interesting!
All of my tiels are comfortable with everyone in our house, but are a little shy around strangers. Even though they will hang out with anyone, they do have their favorites.
Twilight loves Sunset, but he really likes to hang out on me as long as she is near. He is very hands off, but is still a sweetie to me. He gets nervous around everybody else except for one of my daughters, but will still go to anybody if Sunset does first.
Sunset really likes everyone.
Cappuccino really likes me, and is the least comfortable with my two daughters. My husband is just okay in his eyes. He also really likes Niko.
Niko adores my husband, but she likes most people. She's not that into other birds.
All of them were hand raised, and I'm not sure why some are more hands on than others.
Cappuccino and Niko like scratches, but Sunset does only once in a while. Twilight not at all.
I think they all enjoy being around me because I make sure to interact with each of them individually throughout the day.
It is important to make an effort in being part of their day, but sometimes at the end of the day the birds don't care who gives them attention and will like whoever they like.
It's in interesting to hear from a multiple bird home just how individual each bird is, even when raised in virtually the same way and put in the same environment. What about you, do you favor one bird over the others?
There's not much you can do. "Everyone" chooses their own friends. Is it possible to make friends with the "enemy"? Certainly but it has to be "earned" and in cases like this it is a slow process because it takes time. There is no shortcut to time.
Pretty well all the questions you've asked are answered very well in this article. Give it a read.
Site Name - Articles - Behavioral - Sex And The Psittacine
JL, I have read multiple articles on the subject. My goal here is to see what others own experiences with these kind of things has been. Take it as a sort of research. Is it really so easy as just avoiding doing certain things to trigger their hormones?
I understand that things will take time when you aren't the chosen person, but does that have more to do with being "chosen" or does it have more to do with socialization/species/age/and more importantly how they were raised and how they are taught the way things are around the home. Most birds probably aren't used to having more than one person, so when another shows up they are greeted with indifference or worse (or even curiosity, in the bolder birds).
I'm interested in your personal relationships/changes with your birds if you're willing to share with me!
I think as
@JLcribber said, you can improve a not so good relationship but I think the chosen one is the chosen one. I was my tiel's person. He liked other people. Would greet them. Show off for them. Even let them hold him for a bit but he never wanted to stay with them long before he wanted to come back to me. Now, my fiancé on the hand, my tiel initially did not like at all. But with time and patience, they became friends. And Sunny would happily sit with him, nap with him, etc. if I wasn't around. But as soon as I came home, Sunny pretty much ignored him.
I wonder why it is so often that this method works? The favorite person leaves the disliked person and the bird alone and suddenly the dynamic of the relationship changes. It's probably because when the favorite is there, the bird feels protective and must drive off any "rivals" to their attention. But what if it's not so much to do with that but rather socialization or just plain survival? Birds usually live in flocks, learn to live with each other without much fighting. The same should then be possible to attain with their human "flock", if the bird can learn that the more the merrier without driving one or more away from their "chosen". Easier said than done, though, especially since not all people are very bird friendly.
This is very much the case with Buckbeak. He likes me and appreciates me, and we certainly have a good friendship. He will sing for me and perform tricks and occasionally fly to me so long as I'm the only human around. But as soon as my fiance is home, he gets into a trance. He HAS to be with my fiance. The only way he steps up for me when my fiance is in the room is if he thinks I am going to bring him over to my fiance. It's been great, actually - I have Buckbeak to thank for converting my fiance into a bird person.
Indy is more my bird. He is also friendly and sweet with my fiance, but he is more comfortable stepping up and asking for head scratches from me.
I am in the same situation. A family bird that I take care of while everyone is away at work or school clams up around me and other women, but soon as there's any guy within earshot she goes bonkers for em and will even contact call - when, with me all day she's mostly quiet. Over time I've managed to gain acceptance of giving her head scritches and she will usually step up for me, however I'm wary since she's a bit of a "without warning" biter with ME personally haha. I do think that it has a lot to do with the fact that she's met some nasty, non bird savvy women (she's changed hands 4x).
What about you, why do you think your birds have a preference for you or fiancée?
I honestly can't tell you because I live alone and have one tiel. Buddy my first tiel loved men but when she had enough, she always came to me. I have had Bella since she was 7 weeks old and had to hand feed her so I am hers. She will go to people but wants to come back to me as soon as possible. From the stories I have read, I don't think that you can change the bird's "person" but you can take steps to get the bird to accept you.
Have you experienced a change in anything with her reaching maturity? If she has reached it. Sorry my reply is short, feel free to respond to anything else I said to someone else if you feel it could apply to your situation.
Some Parrots like Amazons will choose one person but they should be well socialised so they still get along with everyone
So how do you go about socializing your bird to keep it people friendly? Again, sorry for short response my fingers are tired haha.
