are you talking weaned from Mama kitty milk or separated from Mama b/c they are 2 diff issues.
I've bred Persian cats & German Shepherds & have raised countless #'s of stray mama kitties & babies
If you are talking about eating some kitten mush & weaning off milk, that can be anywhere from 4-6 wks.
I've had a stray Mama abandon her 3 wk litter & we bottle fed for a wk & then they eagerly ate little bits of mush.
With lots of love from the humans, they turned out just fine.
Most Mamas will start getting up from feeding the nurslings around 3-5 wks... some do it later. Just like us, Mamas are different. When the kitties get up & about some, weaning could be near.
If kittens want to nurse non-stop & she does not want to lie there that long, that may be a sign. Some mamas will just stand up & the little one drop off & run after her :LOL
Now as far as separating the family unit, NO, we don't do that until 8 wks & by that time, the pups/kittens are too busy running around to stick by Mama much. It also depends on the litter too. Each one I've had is different.
I just said that I had 1 litter eating a TINY bit of kitten mush & STILL NURSING on Mama @ around 3.5wks... they were not fully weaned until 6 wks... & did NOT go to homes until they were 10 wks old !!!!!!!!!!!!!!!
As far as animals being taken too early...
: that it bad & very common for Puppy mills to rip 3wk olds from their Mama & wean overnight to food because THE YOUNGER THE PUP/KITTEN. THE LESS THEY WEIGH for the 18-wheelers load
so the more they stack many crates hi.
Sometimes there are 100's of animals in these Semi-trucks that do not see light til they get to their