Is kneading catching ?

Hi all ! I have 4 cats and until recently only Pooh was a kneader. She's been a kneader since I got her just over 3 years ago. Well, not long ago my Princess started occcasional kneading. She is 5. This past weekend Pooh's sister Tigger (same age as Pooh) started !

What is going on ?? Should I be worried or happy about this ? Is this a sign of contentment or insecurity ?

I believe kneading is very normal. All my cats do it; some more often than the other. Perhaps Pooh does it a lot compared to the others.

I thought it was a sign of contentment... I certainly hope it is as my 6 month old kitten has recently started kneading more.