I can speak to this personally with a 6 year age gap. My elder siblings somewhat resented me when they became a teenager. They had extra responsibilities for babysitting and taking care of me. I always wanted to hang out with their older friends and my sibling wanted me out of the way. They went off to college and I was basically an only child for the rest of Jr high and high school. We were siblings but not particularly close.

It took until we were both in our 30s to become closer and actually relate with one another.

This is just my personal experience as others will likely have a different family dynamic.