3 month matured kittens sucking on paw? is this ok?? ?

My 3 month old kittens have been chasing down the bigger cats and sucking on the bigger cats paw!! I have heard of them sucking on thier own but on another cats?? Is this safe for them? should I be concerned or simply pass it off as a cute lil habit?? lol please answer!!
this may not be safe if the elder cats are a little bit viscous.
The bit cats might accidentally open a claw out and scratch their mouth.
thats how they clean themselves then they get coat balls after
Answers:    If the elder cats don't mind it, I don't see the problem. As long as they don't lash out at the kittens I think its just a stage they are going through.

I used to hold a kitten that would suck on my hair, really close to the scalp. (he also kneaded the scalp, which wasn't that fun, but it was cute) He eventually grew out of it.

I also have a cat that for the most part of her life, sucked on the end of her tail. haha. She have really long fur so after she was done, most of her tail would be poofy until you'd get ot the end, after it was like a little dagger, just made of fur and spit.
:D
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