They usually open their eyes when they're about 9 days old, so they may not even be 3 weeks yet...
which would mean that they really are infant babies, so wobbly legs & sleeping most of the time would be normal.

(If you want to get kitten supplement, I'd say give it to the mother cat!)

I agree with Sylvia. Sounds like they are just still young and babies. They should be getting what they need from the mother. Just feed her really good and give her supplements if you want to. They will be playing and running around soon enough!LOL

Handle them alot, because if they are not handled now, they will not be socialized and adoptable later.

Please get the mother spayed by a rescue organization, at the very least. Feed her kitten food while she is nursing.

Momma cat will look skinny and scraggly after having kittens.Look what she has been through and feeding several babies is hard on a Mommy.LOL My Vet recommends feeding the mother kitten food for a few weeks before kittens are born and continue until the kittens are weaned.
I hope momma isn't already pregnant again.

Give the mother extra food. It's normal for her to look skinny. Handle the kittens all the time. This is the way they socialize w/ people and turn into trusting animals. At 7 weeks, kittens not handled turn feral.

The kittens are probably 2 - 2.5 wks old. If you do handle them now, wash your hands. Otherwise, socializing can wait till they are about 4 wks old. They are too vulnerable right now, and should do mainly eating and sleeping

IF they cry a lot, then yes, KMR would be a good idea - mom cat might not be catching up
Otherwise, if they sleep a lot, they are content and mom is feeding them just fine

Mom cat will be skinny for some time, as she is spending a lot of time feeding...She will start getting fatter once kittens are not as demanding/eating on their own

Mom needs a lot of fluids: water, KMR, goats milk, wet food - all are very useful

Once kittens weaned, do spay the mom!

Olya

You can and should handle the kittens now. Gently. Always wash your hands after handling any animal.

Kitten food for mom will be sufficient. You can start offering the kittens wet kitten food with KMR mixed in as soon as they begin to explore and stand straight, at 3-4 weeks.

I recommend getting this family off the street into a foster or shelter for the best future for all of them.

Thanks for the replies. They are at least 3 weeks old. We found them on the 5th and they were a few days old then. They do seem to sleep a lot so they must be getting enough to eat. I have handled them probably once a day for the last few days. One of the kittens had his eye sealed shut twice by this gunk and I had to remove it. The mother has an eye that is runny so they probably have some type of infection. I need to take them to the vet (I have an ointment for one of my adult cats that had an eye infection/illness earlier this year but don't want to use it on the kittens as they are so young.) But at the moment I can't afford to take them to the vet (my vet charges a $50 office visit for EACH cat). They do walk around their "house" a little bit to change sleeping positions or to cuddle with each other. Their legs are very wobbly. Their little ears are still sort of flattened to their headds so they are definately younger than I originally thought they were. I bought KMR and have given some to the mama cat (who doesn't care for it). I tried to bottle feed one of the babies but he didn't take to it. I'm feeding the mama cat three cans of wet food a day and all the dry food she wants to eat.

Yesterday when I was holding one of her babies he kept crying and she was very nervous and kept "talking" to him and licking him and he still cried and she started panting really hard like she was nervous. After I fixed his eye, I put him back in the box and he was fine. He seemed to perk up after I got his other eye open. None of them are sneezing or showing any respiratory illness, just have gunk in their eyes and mama's eye is very watery.

The mama cat now tries to run into the house every time we open the door. Seems she wants to escape from her kittens!

Yesterday when I came home from work, the neighbor's dog had gotten loose (this big hound dog) and was in our yard. He was barking and barking. Mama cat (her kittens are behind the house) was in the front yard literaly six inches from this dog's face. She was crouched down and hissing at the dog. But she would not flee. The dog didn't know what to do so he was just barking obnoxiously. I've never seen a cat just stand there in front of a big noisy dog like that before. She will also challenge the neutered male cat (even when he's not near her kittens) by getting right in his face and growling.

Get her and the kittens to rescue before a sad ending to this story. Eye infections are contagious. Hounds kill cats. Toms kill kittens. Really.

Best of luck.