I first met my two cats when there were stray kittens, along with their mother, a sister, and a brother.
In some ways, their behavior has been completely unpredictable. In other ways, they still act exactly as they did when they tumbled out from under my neighbor's house. I swore up and down for months that none of the kittens would ever be lap cats, and now I wear jeans to save my legs from the kneading scratches!
My neighbor thought there were only three kittens, and Athena is the one she missed. Athena hides in my closet, in my cabinet, and does not like strangers. I never would have predicted that she would have bonded with my husband I first, but she did! She trusts me and my spouse very, very much, but never does anything adventerous or dangerous. She got her name by being social when playing with us; she is like Athena, the goddess of war strategy, who will deign to interact with humans when they have war on the mind. She still loves to play.
Artemis was one of the brave kittens, but she never let us get anywhere near her. She is the easy one to spot, but not the easy one to touch. She trusts herself above all others, and is very suspiscious of everything, but she is also adventerous. My spouse is STILL not allowed to touch her, but she demands attention from me at least twice daily. Artemis got her name by being obsessed with insects in the house. She attacked them, and was very possessive of her prey. I named her after the goddess of the hunt, who both loved to kill prey and was very jealous of her personal space and divinity. Artemis is the one who loves looking out the window and makes that hilarious squeaking sound when watching birds outside (or rabbits outside or killing insects inside or...).
I have an analogy to describe my cat's behavior; it is as if Athena is very shy, and as if Artemis is paranoid. If someone had suggested this to me the first day I met them, I would have agreed. I don't know about earlier, but I think cats have obviously set personalities by the time they are out exploring. I never would have predicted their adult behavior (well, I did predict it, but I predicited it incorrectly), but their adult behavior is consistent with their kittenhood behavior.