For me they would have to be older but also 'big me' isn't that old.
For ME, and that's an important thing I think, coz we all have diff needs and desires and cravings. I yearn everyday for that Daddy who will let me be me and live how I wish I could. Being the little and sometimes middle who gets given her rules. Is told yes and no. Has that person know how to set boundaries for me coz they understand me and not just what those should be but how to set them coz they understand their little girl. Any guy can say they're 'Daddy' and just be an a***ole. Not being that kinda person and taking the time to understand us girls ( or boys!) is the dream we look for coz tbh it's far from easy to find. They also get that I might strop or sulk but coz they're older they know how to deal with the occasional brat-me.
For me at least I need that person to be older. Coz the cuddles don't feel the same when there's not that big broad chest to snuggles into ( even if those shoulders r virtual) and little girls are naturally inclined to listen to rules from a Daddy who stands not just taller but older than she is. When i'm in my ickle space sometimes I want to be silly and even though I might not admit I also kinda
the rules but that needs to come from a Daddy who stands over me in his height, his experience and his authority that's shown in the loving way that is natural to him coz he's older than me and has that experience of being paternal
It just wouldn't feel the same for me if he was younger than me. Maybe when im older I might feel diff and im not saying it can't work coz tbh I dont have any right to say so anyway but for how I feel about things it would be a breaker for me.