most likely, white mulberry (Morus alba)..

Yep: asked about repeatedly, because at this stage they don't look like the adult plants

I'd say a mulberry, maybe Morus rubra. Leaves can come in a variety of shapes but that lobed one is fairly common to young plants. Thanks to birds, it can be rather weedy.

Agree with Bill that white mulberry is most likely. At any rate source trees are probably visible somewhere in the vicinity. Otherwise here is how to tell them apart:

www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=121220

In short red mulberry has a rough leaf surface and white mulberry does not.