My youngest brother (about the same age spread) is my favorite sibling, and always has been. But in highschool, I was busy. Homework, writing, sports, drama. When I came home from school I'd essentially lock myself up in my room until dinner. I was either working or exhausted and taking some downtime.
I never understood why some people would tell my mum I didn't seem to like my brothers and sisters much. Fortunately my mum also came from a big family, although she wasn't the eldest (as I was). She'd just laugh at them.
I was NOT my siblings parent, but many people expected that KIND of relationship. Nope. If I was asked to help, I helped. But I didn't parent my sibs. Even if i was babysitting, I didn't 'parent' them. I played, fed, changed, refereed them... but I wasn't their parents.
If they were upset, bouncing off the walls, playing with x, y, z... pretty much whatever, when SOMEONE ELSE was in charge, I ignored them. They were little kids, they were going to do little kid stuff. When one comes from a big family, or there's a big age spread, you learn to 'turn off the noise' to carve out some personal space. If I wasn't "on" I did my own stuff. Sometimes they'd join me, but my parents really respected each child's developmental space and they'd not only keep them from pestering me, they kept them from pestering others (think 2 toddlers for a moment... if they're playing on opposite sides of the room and one keeps trying to drag the 2nd one over to where they are, but the other child doesn't want to go, you don't let one boss and drag the other. You say "Suzies playing HERE right now, you need to let her be, she may want to play later." You don't yank up Susie and say "Play with your sister, your stuff isn't important, she wants you over there." ((But people, not my parents, do seem to do this to teens for some reason. Demand they drop everything because the baby wants them.)). They didn't insist that the 3yo put down their blocks and talk King Lear with me, nor that I would put down my King Lear to play blocks. For my sibs closer in age, our parents had DEFINITELY done the 'let your sister play with you' type thing IF we were excluding them UNTIL we were teenagers. (When 'childish games were put away, left in the nursery'.) Teenagers are just adults without experience to temper their reactions. And my parents never insisted that other adults (aunts, uncles, grandparents, friends, etc.) stop what they were doing to 'play with the kids'. Ditto we were taught not to EXPECT to be included in our other siblings activities. We might be invited, but it wasn't our right to demand the invitation.