www.imageshack.us is a site where you can post a photo without even having to register or set up any albums or any of that.

It sounds like one of two things are happening.
It could be that a maple seed (or something that looks like a maple- box elder, poison ivy etc) has gotten into this area and germinated.

Or it could be that your tree is sprouting from a root.

Either way, yes you should remove it.

Where I am, volunteer maples sprout up EVERYWHERE. They are nearly as bad as Tree of Heaven. Pull those darned things!

I'd transplant them and see what they do in the Fall. Maybe even keep them a few years before making a decision. There isn't much work or space involved.
I grow a lot of seedling Japanese maples and a lot of them are worth keeping, but almost worthless if I were to sell them. People buy named varieties so they know what the're getting. I make a decision whether to keep my seedlings or not in the Fall so I know what I'm saving. I'm more concerned what a tree looks like than the name. The price is right.