Most likely. Are all three kittens nursing mom well? Is your room warm enough? Just want to make sure everything is going well tonight before I head to bed. Do you have any more questions right now? Is everything okay?
Post a picture of the kittens tomorrow and let us know how they are doing!
Yes, it's a problem. Put him on a nipple and see if he will latch and nurse.
If not, ask your mom to get kitten formula at Walmart or the pet store, and a small syringe from a pharmacy, so you can give him some extra food to survive.
I can tell you how to feed the kitten if you get the supplies.