is this odd?

our kitten - who is 4 months old? or so - has been sucking on his nipples alot lately. Whenever he lays down to sleep or is just in a contented mood; he curls up and sucks on one of his nipples and goes to sleep. I've never had a cat do that before; he's obviously happy as he's doing it - he purrs up a storm - but is this normal? or should I try to stop it and if so how?

Any information would be greatly appreciated

Proud momma of many-named cat and Yoshi - a dog (who is, thankfully, wonderful friends with the cat)

Many kittens never outgrow the habit of sucking on something. The "something" can be your clothes, a blanket, your finger, earlobe or some other human body part, or another cat's or their own toe, ear or even nipple.
Unless the kitten is harming himself (which rarely happens as long as he's sucking his own nipple and not another kitten's), I would let him do as he wishes. If you notice the nipple area becoming irritated, you may wan't to consider trying to stop this habit.