Unfortunately we have many stray/feral cats in our neighborhood. I have found many cats and no one claims them. They'll be here but I won't be going around knocking on doors. I'll put a post up on Facebook and Nextdoor though. My neighbors don't care about animalsI ran into this situation a few months ago, mom with babies about the same age. After feeding them for about a week And looking for a rescue to take them, I went door to door with flyers in my neighborhood and the next day they were gone and haven’t reappeared. Some nearby owner apparently let the kittens out with mom and she thought my shed was a good place to hang out and maybe teach hunting.
Might not be the same for you but if you have neighbors be sure to check before assuming they are abandoned.