I found two feral kittens at two weeks of age, one died of pneumonia, the other one seems OK. The vet had me put him on wet food a week ago but he will not drink any water. Does he need water? I have read the wet/ dry discussion but isn't mine too young to go on dry food?

"The" wet/dry discussion? Is there only one?

Age has nothing to do with going on dry food. It lacks the moisture that cats need and most of them do not drink enough water to make up for this lack of moisture. It can end up causing urinary tract problems and kidney problems later in life. All you have to do is think logically about how a cat eats in the wild. There's no kibble in the wild. They eat small animals. And they clean their teeth by chomping on bones and ripping apart meat, not by eating little pieces of kibble that do nothing in reality. (I know people who give raw turkey necks for them to chomp on. Raw is OK.) And dry food is also very high carb, way higher than a cat was ever meant to eat, and can cause diabetes.

Cats don't naturally drink a lot of water because they get most of it from their prey. Wet food has almost the amount of moisture that a cat needs, so a cat on wet food shouldn't need to drink a lot. And you may never notice the little bit they do drink.

If the cat actually seems dehydrated, that's a different matter and could be caused by something else. Their gums should be slippery (not sticky), and if you pull up on the skin at the neck/shoulder blade are and let go, it should spring right back into place.

Of course, what's also natural in the wild is for four week old kittens to be on mother's milk, not commercial food. Since that is obviously not available, do you have in your area kitten milk that you can buy? Or you can try Pedialyte for children and dilute it with an equal amount of sterile water. That's around the age they could start weaning, so that's the time to be introducing solids, not already on them. That is, you could do partial kitten milk and partial food. There are kitten food recipes you can use and I'd personally go for that rather than commercial wet food. You can also give a little meat baby food.

There's a couple of kitten recipes and other info here:
Emergency Orphan Kitten Care

Young kittens can have a hard time surviving without their mother and even with good care can still die. Food and water is not the only thing to pay attention to. Read everything at that link. That's not everything but it covers the main gist of it.

We had a similar problem with our kittens.
We gave them kitten milk and gradually added more and more water to it until they drank straight water.

At 4 weeks old the kitten may not know how to drink out of a bowl either... you may need to buy a bottle from a supermarket or chemist and buy KITTEN milk to feed it.

CATS NEED WATER... if they don't drink water when they are young then milk is acceptable, but if you are only giving the kitten wet food it will become dehydrated.