If you have a pure family, they'll evolve straight into the special family members, skipping the toddler stage and in the case of the main character, the teenager stage as well. Sort of like how if you mate together an Otokitchi and Ojitchi on a previous version, the baby will start off normally but then evolve straight into Oyajitchi.
Here is what I mean by "special family members" and "main character":
Mame Family: Mametchi (main character) and Chamametchi
Meme Family- Memetchi (main character) and Imotchi
Kuchi/Kuchipa Family- Kuchipatchi (main character) and the Chibipatchi
Furawa/Violet Family- Furawatchi/Violetchi (main character) and Kizatchi