I didn't ask something, stupidly, but do you know how old he actually is? I know you brought him home as a hand-raised baby, but is he at least 6 months old or older?
The reason I'm asking is because there may also be hormones at play here, in addition to the fact that you've not had him long at all...Green Cheeks usually go through puberty somewhere around a year old, but it's not unusual for them to start having hormonal behavior as early as 6 months old, it's dependent on the individual bird...And even if it's not hormones right now and it's simply the fact that he's still settling in to his new home and with his new people, he will soon be going through puberty, which is no fun for any parrot owner, trust me...So he's potentially got a lot going on right now...
And as Noodles said, yes, he's a hand-raised bird, but he wasn't hand-raised by you or anyone in your house, or hand-raised in your house...So regardless of the fact that he's not a wild bird and he has a general trust of people and likes to interact with people, he is still going to be uncomfortable with anyone he doesn't know. So I'll repeat this again, it just takes time...But I wouldn't at all start considering re-homing him, because you're going to go through the same growing-pains with any parrot you bring home, hand-raised or not...
***I think that when you first brought him home you were going through something called "The Honeymoon Period" with him, which simply means exactly what it sounds like...When you first brought him home he felt most-comfortable with you as opposed to the other people (men) in your home, so he was biting them and was allowoing you to be his flockmate. That could be because of anything, there's no way to know why he originally latched onto you, but you were the one he chose as the person in the home that he trusted, at least on a temporary basis, but that doesn't mean that you actually had "Earned His Trust", which takes time....And now tha "Honeymoon Period" is over, he's settled-in to his new home, and now he's figuring out the different dynamics between himself and his other new "flockmates"...And if you add-in some hormones to that equation, you've got a 13-14 year-old teenager from hell at home, lol...
This is all about patience, time, and as Laura said it's about doing things at HIS PACE and not at your pace. You can't every force anything with birds like you can with dogs and other types of pets, they are just too damn intelligent. It's like trying to force something with people, usually it doesn't go well.
****I don't know if this has been asked yet, but does he have access to any small, dark places either inside of his cage or that he can get into or underneath outside of his cage in your house? The reason I ask this is because all parrots but especially Conures have their hormones go out of control any time they are inside of a small, dark place or they have access to any type of "nesting' materials...The usual culprits inside of their cages are any types of tents, or the "Snuggle" or "Cuddle" Huts that they sell to hang inside of their cages, or any types of "Beds", like the 'Triangle Beds", or any types of boxes, whether wooden like a nest-box or just a regular cardboard box. Anything that he can get inside of or underneath...As far as "Nesting Materials", this includes ANY TYPES of bedding like wood chips, Carefresh paper bedding, shredded paper, etc. It also includes any blankets, towels, or any other pieces of cloth/fabric that he can get underneath, as sometime people mistakenly put either some type of bedding material in the bottom of their cages, or folded-up towels or blankets...The biggest In-Cage culprits are the Hut/Beds/Tents/Hammocks that they sell in pet shops for birds...
Outside of his cage this usually includes any furniture that he can get underneath or behind, like couches, chairs, entertainment centers, etc., as well as getting underneath the blankets on the couch or bed, or behind pillows on the couch or beds...All of these things can cause their hormones to go crazy and cause horrible and sudden aggression out of nowhere...I had this happen with my own Green Cheek when he was around 2 years old, he had never bitten me once since I brought him home at 12 weeks old, not once, and then one day I couldn't find him and finally found him underneath the couch. He was under there collecting little pieces of things that he found and making himself a little "stash", and when I tried to get him to come out (he's recalled-trained) he refused, until he finally "charged" me, running at me full-steam and latched onto my hand and wouldn't let go, and then did the same thing to my foot. He was absolutely out of his mind on hormones, they're like birdy-crack...I put him inside of his cage for a while and later he was fine again, but all birds respond differently to hormones, and they can really be a serious issue for people...
So just in-case he does have any type of Bed/Hut/Tent/Hammock or nesting-materials inside of his cage, you need to remove them ASAP and never put them back inside...And when he's outside of his cage you need to prevent him from going underneath or behind anything...
Otherwise, it's just going to take time for him to settle-in and gradually give his trust to you...And like I said, if he's anywhere between 6 months old to about a year and a half old, then he's also likely dealing with hormones too, so ensuring he has no access to any small, dark places, as well as making sure he's getting a full 12 hours of sleep every single night will help to calm that issue...
***I recommend that you do a forum search for "Natural Light Schedule", as this is one of the other things that can really dictate whether his hormones are out of control all the time, or whether they are kept under control...
