In the image below (via 秒刊SUNDAY), you can see Sosuke and Ponyo, the stars of the 2008 Ghibli anime Ponyo. Sosuke is the five year-old boy who befriends Ponyo, and the two develop a relationship over the course of the film.
Under that, you can see an image of Mr. and Mrs. Osono, the guardians of Kiki in Studio Ghibli's 1989 feature film Kiki's Delivery Service. Isn't the resemblance uncanny? Well, sorta!
The implication here is that Sosuke and Ponyo grow up, and live happily every after. They opened a bakery and took in Kiki as one of their own.
Of course, this would involve series foreshadowing on the part of Studio Ghibli as well as leaps of logic in both anime, so let's just go with these characters look sort of similar. Though, I'm sure if you want, you can spin this out into an amazing urban legend.