Found cat with two kittens (Salem)

Arrived in my back yard with four kittens about 2 months old around end of July. I have watered and fed and they are getting used to me. I can pet mother cat and two kittens and can pick up kittens to sort them into separate bowls of food. Two of the kittens have not returned in last week. Not feral. Not hissing or scratching. Perfectly willing to just hang out around back yard. Hungry but in pretty good shape. No responses from neighbors or postings on NextDoor and Pet Boost. Would love to find owners of Mom Cat, but would be glad to find homes for one or all.