My experience may not be typical, but just to let you know things can work out...
I TNR and socialize (if possible) feral cats. Years ago, a vet friend told me that the ideal age to "tame" a feral cat was 5 weeks, as week by week they get more feral, as taught by their mother.
A couple of years ago, a VERY feral cat had 4 kittens on my property. We greatly enjoyed seeing the 4 little mites, whom she had (wisely) stashed in a barrel filled with grass clipping to the top, once their eyes were open. They were tiny, but safe from lots of predators. Though I was determined not to increase my indoor cat population, we could not resist peering at them and occasionally running a finger over their itsy bodies.
Mama cat did not like that & moved her babies into the garden foliage, but they tended to totter out into the grass to say hello. So Mama cat decided to get them well away from the evil giant humans, and stashed them under my car in the driveway, next to the street! I could not let them become kitten pancakes, so I snatched them all up. At that time they were 5-6 weeks old and so small they walked right through the bars of the crate in which I keep post-spay TNR cats. (We wrapped it with chicken wire to contain them. Otherwise we would never have found them in the house.)
Yes, we had to bottle-feed them for a few weeks, but they slept in a heap together, which I think helped their feelings of security. I set up a 4'x4' play area for them with toys, dry food & water and let them play there together for 2 or 3 periods a day.
As they grew larger, I kept them in 2 crates, mixing & matching. They still played together as a group. During this time they got vet care and all shots.
I found homes for 3 of them at around 3 months of age, two to the same house and one to a house with a very ladylike adult cat (who was horrified at the rambunctious kitten who loved to bounce all over her. He had to have crate time-outs, but now they are inseperable.) I kept the "leftover" kitten, who dashed out of the crate with glee and never looked back.
What were they like, after being seperated from Mama cat at 5 weeks?
1. ALL used a litter box from day 1
2. They played like little predators, junping on each other and play-fighting.
3. They were all petted and handled several times a day by 2-3 people. All became affectionate and friendly with people. They went to live with people with whom I am still in touch, and I still hear how sweet & laid-back they are.
4. My little "leftover" is the most outgoing of all my cats. Although there are territorial disputes among the related subsets of cats, every cat loves & tolerates her. (No adult cats had contact with the kittens growing up, but they prowled about the crates, so they were very used to their smell.)
I think it is more traumatic for single infant cats to be seperated from their mother, but this litter always had each other, a safe & stable atmosphere and lots of human contact & affection from Day 1 inside, so they have grown into exceptionally well-adjusted (indoor) cats.
So if you have two or more kittens and they have each other to snuggle with, they should do OK.
(Incidentally, none of them suckle. My little one kneads, as do my eldest. Most of the other cats, tamed from feral older, no not knead.)