User blog comment:ACommonCarl/If each April Fools episode is a year, then how does Lily exist during the other three?/@comment-34904882-20180228230454/@comment-34834269-20180301042757

Maybe the Delightful Children's Father spoils them since Sector Z always ruin their birthday cake.

As for aging I wanna say through the seasons they were probbably 8-12, seeing their personalities grew.