Morning all. I'm off to work, slept in a little late since my brother doesn't have school today. They might fire me - oh wait, I'm not being paid yet, and when I do it's by the hour, they don't have much for me to do today, and my dad runs much of the company... no worries, then!
Depends oh how often they do that. As far as I can remember, my parents left us with younger siblings less than five times throughout our (me and my older sister) teens (and they even fretted about that.)
We do that on a very limited basis. Our 13-year-old is, well, 13. So he can watch his younger brother for short periods of time (Mom runs to the store, etc.), but there's no diaper changing involved and precious little else.
My wife remembers being forced to watch her neices when she was a teenager. Her older sister actually said to her (when she said she had something else to do), "well, if you loved them, you would take care of them." My wife's response was "well, if you loved me, you'd pay me." (It didn't change anything, but that's a whole 'nother book.)