Out of the 4 cats we have, 2 daughter and 2 us, all were a rescue with 3 being feral kittens. Daughter's two were found/caught about 5-6 weeks of age and our Kali was believed to be 8 weeks. Daughter's two adjusted immediately, but I also recall the vet saying that we were lucky with the age as 8 weeks is the point at which they have a problem being domesticated. Our Kali, though very loving is that little bit more distant, and I wonder if that little age difference mattered.
Anyhow, your situation. If they are actually 5 - 6 weeks of age, I would expect they would adjust. So I am trying to offer you hope. As for methodology, I hope that others here can be of help.
I did do an internet search on "how to domesticate feral kittens" and saw the following instructions. Don't know if my posting as a cut and paste is a no no, but you would get the same hits using safari and that phrase.
"Give the kitties a safe space. Once you are able to bring the feral kittens indoors, create a safe space for them in a bathroom, spare room or other confined space, where they won’t be around humans, dogs or other cats. Install a litter box (they’ll instinctively know what to do with it) and supply food, water, beds and cat toys. At first, the kittens will be scared to death of you and won’t come near you. They’ll hide when you enter the room and hiss and scratch at you if you get to close. This is all perfectly normal behavior.
Ignore them. If you try to get the feral kittens to come to you before they’re ready, the only result will be hands and arms covered with scratches. When you first start working with them, the best approach is no approach: Ignore them until they’re ready to investigate you. Unfortunately, it could take days or weeks for them to start coming around, but your patience will pay off eventually.
Read to them. My favorite way to get feral kittens accustomed to being around humans is to sit in the room with them and read aloud from a book. The book serves two purposes: It keeps you from getting bored — of course — and it allows the kittens to get used to the sound of human voices. Visit them for about 15 minutes at a time, as many times a day as your schedule allows.
Introduce them to play. With enough time and patience, you’ll find that the kittens will start investigating you — let’s hope sooner rather than later. Don’t grab at them or make sudden moves, which can set you back days. Instead, arm yourself with a couple of string toys, the kind that have a feathery mouse dangling off a short pole — or a laser pointer — and tease them into pouncing on it. You’ll be able to engage with them without having to get too close.
Handle with care! Once the kittens begin to respond to your presence and play with toys, take things a step further by initiating physical contact. Go slow and let them come to you. Don’t grab them, and don’t pressure them into doing anything they aren’t ready for yet. When you are able to handle them regularly, do so as often as possible. Your primary goal at this point is to acclimate them to human touch."