Other genres here Genres Master List
In these fics Mulder and Scully have a living child or children -biological or adopted- who are older than their son William. (and they have William too.)
The Marriage series by Angela W. (note: when prompted the password is "avalanche")
Family Matters by Devin
Daycare by Devin
Gum and Note Passing by Devin
Sweet Sixteen by Devin
Who Knew? by ElleThom
I Should Have Known by ElleThom
When She Came Back To Me (aka 96 hours) by Lizzy
William's Fifth Birthday by Erin Blair
Beyond The Truth by Neoxphile
Goodwill Towards Men by Neoxphile
The Family G-Man by Neoxphile and FelineFemme
Mandy by Pattie
After Mandy: Bobby by Pattie
Alison by Pattie
Tell 'em William Called by Pattie
New Year's Revelations by Pattie
The Nursery Files