Ok that makes me feel better... I have three and (14,15 &18) I've been around for 7 years while they are all generally nice, 1 is just a pleasure to have around the house, helps with the chores, helps with our toddler, keeps the room tidy etc nothing is too much trouble.
The other two are lazy (literally to the point of eating out of Tupperware is all the bowls are in the dishwasher etc ) the room is a state, unless directly asked to do something they would happily sit on games all day Thursday- Monday unless to pop their heads down to see what's for eating or to demand dads attention.
All this I can mostly ignore but I find myself treating the helpful one to much more ie, I bought some new expensive trainers as they were saving really hard for a pair so I said it was my treat this time, they all get pocket money but I sent this child more most months for the help they do such as they watched my son for a few hours when I was really busy and 1 hour turned into 5/6 (dad was working) I kept calling to check they were ok and they had made lunch, took him on a walk etc I was so grateful that I sent them £20 as I said they don't come to ours and be expected to babysit for that long, bearing in the the other two didn't lift a finger to help at all but happily moaned about not getting money.
I've now been accused of favouritism by the in laws (jokingly but seriously also) to which I said (not around the 3 kids) yes I do have one as it's pretty bloody hard not too! And if I want to go above and beyond for this child because they deserve it I will, I don't feel the need to treat everyone equal when they don't act equal.