Yes a child can have dimples even when both parents do not have dimples.
Dimples are sometimes inherited but most times dimples are also caused by fat in the babies cheeks so if your baby has fat cheeks when born then they might have dimples.
A friend of mine has a child with dimples and neither him nor his wife has dimples so yes it's possible for a child to get dimples without either of the parents having dimples.
Dimples can also be passed down from some other family member through genes.