Honestly? My sister and I have same bone structure and skin type except I'm very fair and she's very dark.
I burn quickly so I've always stayed out of the sun, she's out in it every chance she gets without any protection as she never burns but won't listen to "skin cancer scaremongering"
I also have mainly drank water for about 15 years and been mostly caffeine free for almost 2 years (New Years resolution, occasional "slip"), she is a caffeine addict (caffeine is a diuretic/dehydrator)
I'm nearly 5 years older than her, when people don't know who's the eldest usually as they meet us through mum, they assume she's the elder sister. Which really pisses her off! 
I'm 48, I've genuinely had people disbelieving I'm even in my 40's - I'm not saying they're right!
My skincare "regime" consists of face wipes and basic cheap moisturiser twice a day which is all I've done since my 20's.
No fancy expensive products
Also I've been veggie for over 30 years and I'm generally speaking a fairly healthy eater I'm not a fan of junk food finding it generally bland and unsatisfying and I can cook something in 20 mins (less time than it takes to order and receive a takeaway around here) that is tastier, healthier and more filling.
I've observed of others with youthful appearances that they generally speaking just lead healthier lifestyles.
Mostly veggies I'll admit but the meat eaters who fall in the same category eat fresh, unprocessed meat mostly (I'm not talking expensive organic grass fed etc just will have a piece of chicken breast as opposed to a frozen breaded type for example)
And they generally are sun avoiders too
Hope that helps?