Unknown Brother and Sister?

So I found a bunch of Photos hidden in an Album, but they are not labeled.

Does anyone recognize this photo of kids; they appear to be sister and brother or close cousins. at the bottom it says C.F. BROCK Athol, Ma

They were in my Grandma's Album.

I'm hoping someone can help tell me anything about them.

Who are they? When was this taken? Do we have any information about them?