As I mentioned, I read a bunch of Emma backstory comics, starting with Emma Frost (2003), and it got me on a character design kick. Before starting to draw Emma's journey, though, I actually went and sketched her whole family!
The second image (of which I've already posted the Emma bit) is from the scene at the end of issue #6 where Mr. Frost names his successor. It was previously depicted in New X-Men #139, and later again in Dark Reign: The Cabal, but I didn't really take other depictions into consideration - not for this scenes in particular or the characters in general.
I have a pretty solid idea of how Emma currently looks (and I've drawn it not long before starting this), and I know what she's been said/shown to have changed (bleached hair, nose job, breast implants). I took that, and the way the characters looked in this particular comic, into consideration.
I started with the parents, giving them different enough traits that I could mix and match for 4 other characters, and also that Emma could inherit, either to keep or to dislike enough that she'd change them. And then I took those pieces and built the kids. I know that's not really how genetics work, but if I'm (re)designing an entire dysfunctional family you bet I'm taking the chance to get slightly philosophical with it. So:
Winston has brown hair, a smaller face, a hooked nose, small eyes, very thin lips, and a few moles.
Hazel has blonde hair, a longer, thinner face, a button nose, larger eyes, slightly fuller lips, and a more prominent chin.
Adrienne has her mother's hair, face shape, and nose, but her father's eyes and eyebrows, and also a single mole near her lips. She got all her mother's Pretty Girl features, but has her father's cutthroatness. On top of that effortless beauty, she also has a tan and fuller lips, because her appearance is something she takes pride and care in, and is definitely not above going an extra mile for it.
(I know in Adrienne's other appearances her hair is brown, and the common interpretation - or at least the one that made it to the wiki - is that she's a natural brunette who used to bleach it, but 1. as I said, I was going just by the 'Emma Frost' comic, where she's blonde the whole time, and 2. I think it's far more interesting if she naturally has all the things that are iconic - but artificial - in Emma, since she's clearly a dark reflection of her character)
Christian has his mother's hair, face shape, nose, and eyebrows (though harsher versions), and his father's eyes and lips. They're almost exactly the same features from each parent as Adrienne, but he's The Son, he's not supposed to take after his mother.
Emma has her mother's eyes and eyebrows, and the rest is all her father's. Her looking the most like him works twofold: it gives her physical traits to feel insecure about (and eventually change) and creates a direct connection between the two, since he's gonna chose her as his heir.
Cordelia has her mother's nose, eyes, eyebrows, mouth, and chin, and her father's face shape and moles. Unlike Emma, she got so many of the Pretty Girl features naturally, but goes out of her way to reject them. I like to think she probably dismisses all her conventionally attractive traits and instead focuses on small things she's insecure about, like the moles.
And, once again, if you read all of this you get a bonus sketch!
It's from a scene in X-Men Origins: Emma Frost (2010), because I wanted to draw Emma with Hazel before she got sick, but it didn't really fit in the other post (which was exclusively about Emma and starts when she's already a teenager). Not sure how en vogue pinky drinking is atm, sorry if Mrs. Frost looks tacky.