I have five siblings, all (much) older. I have three brothers and two sisters. My eldest brother is 21 years older than me, my sister, the next youngest to me, is 10 years older than me.
My relationships with them vary though I do find the age gap is not the reason for this despite what people think, except in the case of my sister (the one who is 10 years older). We were close when I was little but she was a difficult teenager and without going into it, her antics really affected my childhood and pretty much impacted every aspect of my life and continue to do so all these years later. She had kids young, she did OK with that, but when I got older I think she started to feel jealous that I got to be young whereas she chose to be a mum. We have over the years thus become very volatile towards each other and I will admit I antagonised it as much as she did. We're also just very different people. We had a fight last year and only recently just started talking again. But as much as were different were very similar in that we're both very stubborn and headstrong- a toxic combo lol! But I have three beautiful nieces and a lovely nephew from her who I love and I love her because she is still my sister.
I get on mostly well with my other sister, not much to say there, though we're not close. I have most in common with my eldest brother funnily enough despite our age difference, but we haven't always gotten along. I get on best with the youngest of my brothers. The middle brother is a long story I won't get into but he is kind of estranged from our whole family. I do miss him though.
Despite the complications of having a big family, I'm glad I have all my siblings. I probably wouldn't change anything.
Edit: I also technically have two step sisters and a step brother but I barely know them, we didn't grow up together and we're all adults