Interesting thread - thanks
So I'll put my hand up and say now I'm mid 40's I think I'm the sort of person you're talking about. I'm pretty. But I only really realised this watching my children grow. I think all children are beautiful when young. The cuteness. Cute can pack up and go when they hit teens and there are some very ugly teens (whereas there are no ugly children).
DD is 13. She is cruising the teens (as did I), she is stunning - even features, clear skin, long lashes, symmetrical which is a proven theory to beauty. She mostly looks like her DF side of the family but is thankfully blessed with my slenderness 
Her uncle was often model scouted. And like him, she is utterly appalled by such things. She is shy. Photo-phobic, quiet.
DS is 10. He looks like me, so much so in photo's of the same age we are a mirror. Even our expressions. His eyes are his paternal grandfathers blue though and they are piercing. He's outgoing so I have taught him he is good looking using Derek Zoolander as our guide
. Confident but self depreciating.
I tell them both they are attractive etc. I don't over do it. And I tell them that no one will ask them out because they are too good looking so they should be brave and tell people they fancy them. Age appropriate of course!
When I was young, teens and twenties - when it mattered - NOBODY asked me out EVER. Everyone around me got asked out or whispers rumours abounded that so and so likes you. This never happened to me ever.
When I meet people from that era now, I've been told several times how much they fancied me back then.
But because they never told me, I have gone through life thinking I must be ugly. To this day I don't get asked out (single) except by jumped up arrogant unattractive men. Nice men still don't ask.
AM I being boastful? No. It's taken me this long in life to realise that I am pretty and lots of men think I am pretty but they don't ask me out. So my self fulfilling prophecy continues looping. Every partner I've had is told by their mates they are punching.
It's really annoying actually.