Question are dai cirno clownpeice and the other 2 girls kids?
In canon they are all probably older than kids, cirno was at least 60 I believe, but they rarely specify anyone's age in touhou. But in fanarts artist represent characters in many different ways.
Fairies are immortal, basically humanoid projections of the life force/magic of nature in Touhou. This is why even if they are destroyed, they just reform, so long as the forests or seasons or whatever aspect of nature that generate them still exist. (Cirno, as an ice fairy, is made of ice and a spirit of winter, which is why in PCB, she's delighted that the winter has continued past its natural endpoint.) None of the fairies have listed ages, it's just that Cirno mentions remembering something having happened 60 years ago in PoFV (which is from about 15 years ago itself, now), she is presumed to be much older, and potentially older than recorded history or even potentially as old as life on Earth itself. Fairies also range in size from "doll sized" to the size of a child (meaning Cirno and Daiyousei, whose fan-given name just means "big fairy", are as big as fairies get), and "never grow up" physically, in spite of being potentially ancient. In Cirno's case, this includes mentally, as well. The Three Mischievous Fairies are strange and unique in that they actually learn and try to "play house" and behave more like humans.
