I did the same when I was a kid....13 year old found a kitten wandering around whilst doing my paper round....asked at a few doors ...nobody new where it came from ....so it went in my paper sack and came home with me...lived till he was 15....
About a year later me and my mates were up the woods and found a cardboard box with 5..or 6 kittens in....that came home with me....mum and dad said fook right off...not again....called the cats trust...or one off these charities and they took them..