Is this to much too early?

So I'm a 15 year old and about ready to enter into my sophomore year of high school and during the summer I work 7 days a week from 7:30am-8pm. I am a full time babysitter for my aunt and uncle who work on the family farm. I am with the kids more than anyone else and often I feel like a single mother of two and 15yrs old. It is very hard because I feel like I am pretty much raising them and I am scared to fail them. My aunt and uncle work very very hard and they don't get times off, but some days I feel like this is just too much. I also feel like the kids never see their parents and that's an important part of their life's at this age (4 and 2 ) do you think there's anything I could do? All opinions and suggestions are welcomed! ☺️