Having bad breath is common and does have potential to go away. At an early age, under the age of 3, it's not uncommon for a kitten to experience periodontal disease. In fact an average on 70% of cats under the age of 3 experience it.
This comes from a plaque buildup if remained unchecked. If you are concerned about this, it's recommended to brush their teeth regularly, and begin at an early age to get your kitten into the habit. There are particular brushes and tooth pastes to look for specifically for cats. Methods such as picking a time when your kitten is worn out, not overly restraining your kitten, taking it slow and always treat afterwards to keep the situation positive, are all key to keep in mind.
Another alternative to this is to feed a high-quality food. Looking for some labelled 'Kitten-formulated' as it can carry certain proteins and vitamins, versus those needed for adult cats. It's just important not to only offer dry food as well, wet food offers particular vitamins and minerals that you can't get out of dry food.