I am the eldest of six though three are half siblings from my dads second marriage and I love coming from a large family.
I was asked to babysit a lot in my teens for my youngest siblings, but at the same time, I was always allowed friends around to hang out while I was doing so and free to say no if I had other plans. To me, family is all pitching in when needed, despite age.
Now we are all adults, we always look out for each other. I am closer to some siblings than others but none of them would turn me away if I needed their help with something - but there is such a large range of ages that it makes sense that I would spend more time with my sister who is close to my age than with my younger brothers who are a decade younger than me.
It has affected us differently in our own life choices though - We were quite poor when we were young (me, my sister and eldest brother), though we were always fed clothed. My mother was a stay at home mum, so had more time to play with us and utilise free/cheap means of amusing us, salt dough, bowls of water outside, long walks to the library and back etc whereas my sister and I both work full time.
My sister goes above and beyond to make sure her children never want for anything, even if that means getting into debt, because she never wants them to feel like we did - "Must not ask for that as we know Mummy doesn't have enough pennies" whereas I am more of the opinion "Well it never did me any harm to learn the value of things" and wouldn't put myself in a worrying position financially at the expense of saying no to some requests. That's probably the difference between being the stoic responsible eldest and the overlooked middle child haha.