Maple seedlings are possible, otherwise you should ask after true leaves emerge.

I found a picture, they look like this, when I let them grow more. I remember why these weeds are here. The neighbors have a Japanese Maple and it drops leaves in my yard, so this year, I was like "I can compost these leaves in my compost bin", but this is what happened. Never again, now they have to go in the city compost bins. It too bad, as at my other house, I have great results with composting the leaves of my Asian Magnolia. I'm too old to do all this weeding, my back is messed up. I never allow my weeds to go to seed, and last year I did not compost the Japanese Maple Leaves because I was too busy.

Nice!..they are Acer palmatum seedlings looks to me. Most people wish they had that problem. You could pot them up and sell them.