Next gen; The matchmaker will start coming to your tama some time between the ages of 6 and 7 until age 10 or 11 3 times a day. You can accept the mate she brings to start another generation. Or, if you have 2 tamas, and one is a boy and the other a girl, they can (when old enough) have babies and move on to the next generation.
Taking care of it differently; If you take "bad" care, you will get more unhealthy characters. Good care will get better characters. Kepping the hearts full and keeping your tama healthy and at the correct weight are all things you can do to get better characters. Even if you don't like you current character, it will grow and evolve into others once every few days.
KM