What is the best age difference between 2 siblings in your opinion and why?

My older brother and I are ‘Irish Twins’, we are the same age for twelve days each year and we were best friends growing up and still are very close, he takes me out for lunch and things. Our middle sister and brother are 14 months apart and go through phases of BFFs to not caring much about each other. Then the youngest two are twin girls and are very very very close. But then I’m 6 years older than the twins are we are incredibly close. So we all have our ‘buddy’, but really all of us are close to be honest, and the gaps vary from 7 years to 30 minutes 😊
But we lost both parents and it’s just the 6 of us living all together by ourselves, so that may explain it. The twins even call me ‘mama’ now.