I put together a list of cases where parent and (under eighteen) child or children disappeared together (not counting the family abduction ones):
Four-year-old Aqueda Arias and her pregnant mother, Guadalupe Castro
Five-month-old Marx Barnes and his mother, Charlotte Moriarty
Six-year-old Abby Blagg and her mother, Jennifer (later found dead, husband convicted of murder)
Two-year-old Kimberly Boyd, her mother, Sarah, and a friend, Linda McCord (neither of them listed on Charley)
Six-year-old Cynthia Britto, her mother, Wendy Camp, and her aunt, Lisa Kregear
Six-year-old Barry Brown, his brother Brandon, his sister Sheketah, and their mother Carolyn (father later admitted to their murders, found not guilty by reason of insanity)
Four-year-old Rosa Camacho and her mother, Rosa Delago (later found murdered)
Seven-month-old Jasmine Collins and her mother, Melissa
Eleven-year-old Haleigh Culwell and her mother, Kimberly Whitton
Four-month-old Jeremy Dages and his mother, Bonnie
Three-month-old Selah Davis, her mother, Sasha, and a friend, Jarib Bennett
Three-year-old Ptah Diamond and his father, James
Thirteen-year-old Neil Alan Eddleman, his father, Neil Wayne, and a friend, Gary Lisk (later found dead)
Two-year-old Claudia Jareth Guillen and her mother, also called Claudia
Six-year-old Julie Guthrie, three-year-old Timothy, and their mother, Leslie
One-year-old Royce Henson and his mother, Kathleen
Two-month-old Sausha Henson, her sister Shaina Kirkpatrick, and their mother, Kimyala Henson (later found murdered)
Five-year-old Alex Hernandez and his pregnant mother, Evelyn (later found murdered)
Fifteen-year-old Michalle Houchman, her brother Mitchel Salomon, and their parents Elaine and Sol Salomon (family not listed, suspect charged with murders but acquitted)
Four-year-old twins Brent and Brenttany Hughes, their sister, Sarena Glenn, their mother, Robby Hughes Floyd, and their aunt, Jennifer Hughes
Six-year-old Madyson Jamison and her parents, Bobby and Sherilynn
Five-year-old John Jacobson and his mother, Sandra
Ten-month-old Michael Johnson, his sister Sheri, and their mother, Freda Denman
Seven-month-old Kelsi Krum and her mother, Kelli
Three-year-old John Nguyen, four-year-old Kristina, and their mother, Van “Stephanie” Nguyen
One-year-old Isabella Pastrana and her mother, Holly Codario (later found dead)
Six-year-old Rene Perez and his pregnant mother, Cecilia Newball
Fourteen-year-old Danielle Pitcher and her mother, Dorothy
Five-year-old Grace Reapp and her mother, also called Grace (father charged with murder, but died before trial)
Two-year-old Masaraha Ross and her mother, Ronkeya Holmes
Seven-year-old Daniel Santiago, his brother Noel, and their father, Victorio
Fifteen-year-old Bethany Sinclair and her mother, Tina
Nine-year-old Sarah Skiba, her father, Paul, and a friend, Lorenzo Chivers
Eleven-year-old Nicholas Smith and his mother, Edyth Warner
Two-year-old Daniel Spangle and his mother, Denise Fagot
One-year-old Fannie Stuart, her sister Jessie, and their mother, Mary
Seven-year-old Christopher Szczepanik and his parents, Jaqueline and Vanderlei
Eleven-month-old Shannon Verhage and her mother, Rachel Timmerman (later found murdered, an acquaintance was convicted)
Three-year-old Brandon Wade and his mother, Paula
Bonus batch:
Seven-year-old Angelica Livingston and her grandmother, Portia Washington
Nineteen-year-old Suzanne Streeter, her mother, Sherrill Levitt, and a friend, Stacy McCall
Eleven-year-old Annette Sagers and her mother, Korrina Sagers Malinoski, who disappeared from the same place almost a year before. Annette left a note saying her mother had come to get her.
Not all of them, certainly, but all I can think of at the moment.