I am the youngest! (Not often I get to say those words these days!)
One of my sisters is only 6 months older than me (work that one out!).
Actually the reason is that she's my step-sister. I have another older step-sister (my sisters are 31 and 34 respectively). I also have a brother, who is my 'real' brother, who is 34. So all 4 of us are similar ages, which was fun (not!) when growing up. We all get along very well as adults now though!
Like a fine wine, one gets better with age.