Generally you can change the characters by using certain training items, as ilovekuchipa555 said. But this shouldn't change the family type. To change the family type, you have to mate certain adults to get the Royal Family on the v5.5. I think one possible combination is your Prince Tamahiko + Rosutchi. (You must have 100% bonding at the time of marriage for this to work.) Another way is to mate two characters from the same Tamagotchi type (I think one type on the v5.5 is the Sociable type) and hope that they only have one or two children. Your Tamagotchi's family type should now match the type of your Tamagotchi's parents and should stay the same if you use the right type of training items for your Tamagotchi's life. Sorry if that was confusing!