I have a wild cat that had a litter of 4 and now 3 weeks later 3 of them have eye infections in one eye what can I do

Keep wiping it with a clean warm wet cloth unless it is more serious.

Got to go to the vet. Unfortunately, other than warm water to clean the eye, there isn't any product over the counter that will be safe for a cat's eyes. It's normal for a kitten to get eye and ear infections that young, no worries, the vet will probably just prescribe you an ointment to use on all of them for a week or so and they'll be all better :-)