Nemesic, For me thats about impossible to guess. You dont state if these were purchased from a nursery as grafted cultivars or are they seedlings from under a friends tree. Anyway i wouldnt prune those little babies if the were mine.You have a long way to go with them.
AL

Hi AL,
Thank you for replying.
I did not purchase them, I collected them in Maple Street/Santa Rosa/CA. I though we could identify them with their leaves :(. Ok, then I won't prune it. Hope it grows up. I love JM.
LT,

Given the size of the little creatures, they look to be seedlings. ANY Japanese maple seedling regardless of parentage is considered just a form of the species, Acer palmatum. No cultivar designation. All named cultivars must be asexually propagated, either by grafting or, less frequently, by cutting.

You won't need to worry about any pruning for several years :-)

Thank you very mucn Gardengal48 :-).