Caboose, your second post sounds a lot better than your first. Good!
Sometimes we have to sit and think about what we have, rather than what we don't. Sometimes it is very frustrating.
Don't worry, or compare yourself to those gals who seem to have everything handed to them. They do not, and will not appreciate what they are given. I mean, don't you value stuff you paid for yourself a ton more????? It's part of the growing up process. The reality of it will hit them too - someday.
As far as '"rent." That's just a term your parents came up with. They could have said, you have to pay for your horse. Which, as you know, is waaaaaaaay more expensive than your rent. Take pride in the fact that you are able to help your household. It may eventually even shame your younger sis into behaving properly.
It sounds to me like your older sisters know you're on the ball.You are not alone, your work is not unnoticed. That always makes you feel better.
Last thought - life is unfair. To everybody. Always. We learn a set of rules - call them morals, ( our laws are based on our basic morals) that help us figure out what to do. Beware if you start to really believe that life is unfair just for you. ( Not saying you feel that way.) This is very dangerous thinking. You never know what is going on in other households ....it's like seeing somebody with a gorgeous horse. You are a tad jealous ....resentful that your $600 buddy doesn't look like that $10,000 beauty. IF you don't turn away resentful..... notice that "beauty" switch her tail? The ears go back, and the "my horse is better than your horse attitude girl" is now flying heels over helmet. Thunk! And then that gal sits up, looks at your $600 hose, and thinks, "Why couldn't I have a nice horse like that?"
"There ain't no vaccine for stupidity* Maxine