We know Muggle parents can have a magical child, but could magical parents have a Muggle child?
Depends what you mean by 'Muggle'.
A Squib is a person with no magical powers born to magical parents. They fall somewhere in between a wizard and a Muggle: while unable to actually perform magic, they can still access the magical world. From the Pottermore fact file:
Humans with little or no magical talent born into wizarding families, who are looked down on by the wizarding world
Appearance: Usually dressed like the rest of wizard-kind
Magic Abilities: Able to access the wizarding world, unlike Muggles, and can use certain magical objects and creatures
We even see a couple of these in the main HP stories: Argus Filch, the unpleasant janitor of Hogwarts, and Arabella Figg, the cat-loving neighbour of the Dursleys. But according to Ron, they're not very common:
A Squib is someone who was born into a wizarding family but hasn’t got any magic powers. Kind of the opposite of Muggle-born wizards, but Squibs are quite unusual.
-- Ron Weasley, HP and the Chamber of Secrets
See also Is a Squib a Muggle?