Could be hunger, especially since it sounds like the ones in the past that you fed were quiet(er) and the current batch you can hear meowing.This is what makes me think about this stray family, that are they making noises because they are hungry, or is that just their family discourse! ?
For the strays that come by our house, the only time we hear them make noise is if two males get into territory games and start howling at each other. So I then go outside to chase them off - we live in a neighborhood and the houses are fairly close to each other.