I adopted three kittens from different litters, all roughly the same age and raised them together.
The oldest, a girl, arrived first and spent her first solo 10 days mostly hiding in her carrier during the day, but became quite affectionate in the evenings and wanted to be touching me all night when we slept.
The middle boy instantly shot out of his carrier and did a zoomies tour of the house at super speed, started tearing apart the kitchen looking for food, and scaled every human in sight to cuddle around their necks.
The youngest boy spent the entire first month asleep on my chest, only waking enough to eat and use the tray.
Now at 13 the girl goes off to spend the day alone but wants cuddles for a couple of hours before bed. Middle boy calmed down a bit but never stopped constantly trying to steal food and I have to lock everything up, even bread and veg. He's a velcro cat and wants to be in your lap 24/7 unless there may be food. The youngest grew to an insane size (almost a meter long and 12kg) but spent every day on his back pressed up against the thigh of whoever was sat on the sofa. He wanted to sleep on your chest still but knew he couldn't fit anymore. Sadly he died at 11 of a brain tumour.
There were some minor changes, the girl got a little less timid, middle boy calmed down a bit, and younger boy would actually wake up and play a bit. But their personalities were mostly on show from day one and stayed stable for the next decade+