My toddler gets canker sores in his mouth when he was ill he had like three is it possible for him to have herpes 1 even if his parents dont?

Yes: Bur that depends upon the other individuals with whom he has been in contact. Does he go to daycare? Has he had baby sitters, has anyone put their fingers in his mouth or kissed him on the lips? Canker sores, however, generally appear somewhat differently than herpes ulcers and a pediatrician can often tell the difference.

Yes: Getting mouth sores does not have to be genetic. Herpes is a virus that can be picked in many places. Could be source of sores. Canker sores are opportunistic or triggered by something like foods. Just body reaction. These all can more likely occur when ill, defenses down.