Only criticism I have would be the sizes - adult / young adult look almost the same size, and the ko looks too big relative to the other two. Imagine that adult giving birth to that koyukkuri.
The expressions are neat though - blissful optimism in the koyukkuri, energetic arrogance in the young adult, and some humility in the adult.
Yeah, gonna agree with Kodoku. THe sizes are a little too close, also, they grow taller without growing wider. I dunno if that was intentional or not...