interesting thing about kittens. When they are born, they imediately seek out a nipple. That becomes their nipple from then on. When we had a litter of kittens, the last to be born got one of the nipples higher up on the mom (closer to the mother's head). Anyway, this little guy was the runt of the litter and was a yeller like Nemo. He finally figured out that he could steal milk from his brother's nipple when his brother wasn't paying attention.

You might want to make sure that the mother is getting enough nutrition because by now, she is having to produce a lot of milk for her babies. She needs to be eating kitten food because of the extra calories. You can also start to supplement with condensed milk that is partially watered down. I've heard that you shouln't use regular milk because it really doesn't have enough calories since thier tummies are so tiny and can't hold that much liquid at one time.

good luck.