Well, I wouldn't buy that potting soil again - it came with its own seeds. They do look like a pea or some legume, but it's not possible to tell with only two leaves. With many plants the first two leaves are not the "real" leaves,. You don't see those until they put out leaf #3 and #4.

You don't have a bird feeder in the area do you? Those could also be sunflower sprouts.

I believe these are sunflower sprouts. I have them popping up in some of my containers this year. I think maybe the mice and chipmunks hid some seeds in my leftover potting soil from last year! Little buggers!

Yes, I now believe you're both correct that they are sunflower seeds. I let a couple "orphans" grow to figure it out. I'm thinking now that the birds are dropping them from all the neighborhood feeders. For some reason they're only landing in the pots and not the sfg areas, thank goodness. Next year, I may let a few grow and use them as trellises...lol