Harry and Ginny Potter:
James Sirius: 14
Albus Severus: 13
Lily Luna: 11
Ron and Hermione Weasley:
Rose: 13
Hugo: 11
Bill and Fleur Weasley:
Victoire: 17
Dominique Nymphodora Weasley: 16
Louis: 15
Percy and Audrey Weasley:
Molly: 17
Lucy: 16
George and Angelina Weasley:
Fred: 14
Roxanne: 14 (both twins)
Draco and Astoria Malfoy:
Scorpius Hyperion (yeesh): 13
Remus and Tonks:
Teddy Lupin: 19
They may be different ages throughout the book