They both remain in custody while inquiries continue, police added.
The dog was seized and destroyed at the family home.
One family member told the the dog, called Hunter, had never shown any form of aggression and it was out of character.
Another family member said the mother of the injured baby was “devastated”.
They added the dog and the baby were like “two peas in a pod”.
Police said officers would remain in the area while inquiries were carried out and to provide reassurance to the local community.
