I was just checking some dates of the debut of each member of Emma's family
Cordelia Frost - Gen X #3 - 1995
Adrienne Frost - Gen X #48 - 1999
Winston Frost - New X-Men #139 - June 2003
Christian Frost - New X-Men #139 - June 2003
Hazel - New X-Men #139 - June 2003
Emma solo - August 2003
Is funny to think that Cordelia was the first introduced. And apparently they were already thinking on expanding on Emma's past, since from Jean Grey's invasion of Emma Frost's mind till her solo debut is only 2 months apart.
Also even with the covers pushing away some readers from picking up the issues, the solo is well loved and a lot of authors keep referencing and building upon it, which is rare now a days when a lot of things that happen outside the main book gets ignored.