How do you know when to take care of abandoned kittens?

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I am not entirely sure if the kittens are abandoned by their mother, but I do know that the mother is not any one's pet. I found them next door today, shivering, in the yard of an abandoned house. One has slight eye discharge and I can't tell if they are skinny or not. I am worried because about a year ago I found two kittens around the same age, a week or two, in the same yard, I thought the mother would come back so I left them. Then a few days later we found them dead and kind of eaten by either birds or ants. I don't want to take it from its mother if she does come back but then I don't want them to die. I have experience raising very young kittens, but I just don't know if I should leave them or take them? I'm also worried that one of my neighbor's kids will do something with them as they constantly go back there to play or throw stuff in the window to break the glass. Any advice would be great. Right now I just left them there, I'm going to check on them later, but I have to watch out that my dogs won't do anything because they try to stick their little paws through our fence.