What you need to know that your puppy should never leave its mother and litter mates before they are at least 8 weeks of age. It frustrates me to read a behaviour related question, to then find out that the dog was allowed to be removed from the mother and siblings before the age of 8 or 9 weeks old.hat you need to know that your puppy should never leave its mother and litter mates before they are at least 8 weeks of age. It frustrates me to read a behaviour related question, to then find out that the dog was allowed to be removed from the mother and siblings before the age of 8 or 9 weeks old.