450g is about the weight of a 4-5 week old kitten so either all of your kittens have been severely undernourished, too young to leave their mum, or you're misremembering
Yes I know what the weights they “should” have been for their ages. All of them were vet checked, one before coming to live with me (saw vet record) and again after coming to me, the others after they came to me.
Ages confirmed as correct, were all stated healthy but small, so I’m not misremembering anything.
3 of those were farm cats.(two different farms)I don’t know if that makes a difference. The first one who is sadly no longer with us. Weighed in at 1.3 kg at 6 months old. I had to make sure the vet would actually spay her at that weight. Again her age was confirmed as correct.
The two sisters I still have came from a litter of five (other three were boys). Now 8 years old, One weighs 4.5 kgs fully grown is solid and chunky. The other weighs 3.1 kgs and is very petite.
The last one we have born from an accidental litter was from a litter of 7 all girls all the same size (mum was small as well) she now weighs just under 5kgs at 6 years old, She’s a bit of a heifer!
They’re all still the ages they are supposed to be and all still pretty healthy, there’s never been any deviation from that.
So yes it can and does happen. Doesn’t always mean someone is wrong!