My adult cat kneads and sucks on my blanket like a kitten. Why?
I have seen this behavior in kittens before who are nursing with the mother. They push and pull on the mother's fur with their paws to get the milk. My cat, however, is a adult and has no mother. She does this while purring loudly and it seems to make her happy. Is this is memory that she is re-enacting? Is it a self-soothing behavior? I know little about her before I found her and her siblings abandoned, seven years ago. She was very hungry back then.
Some cats will knead in mid-air if they're feeling particularly pleased. I suspect it as automatic for them as a smile is for us. Suckling is less common but not uncommon.
I have heard that cats that were improperly weaned are apt to display this behavior. That seems consistent for your particular cat... It was so long ago, I don't remember where I heard that, and I didn't look into whether that may be the case.... YMMV
"In adulthood, a cat supposedly will knead when it's feeling happy or content because it associates the motion with the comforts of nursing and its mother. Adding further weight to the explanation: Some cats even suckle on the surface they're kneading."
When it comes down to it though, no one knows for sure why exactly some adult cats knead.
My cats usually want to knead my stomach for a while each night before curling up next to me ; I've always presumed it was memories of mama-cat. The more surprising thing is that they knead in different places, consistently, perhaps because they were in the habit of going for particular teats. It's actually a bit annoying since the big one leans hard, but it seems to please them, so... If I'm not there they'll kneed the blanket, which might even be useful in creating a soft spot.