Any ideas what this plant is?

I grew tomato’s, cucumbers (markermore) and mini peppers in new seedling soil and in a propagator and 3 plants emerged.
One for sure is tomato, the other in pretty sure is the peppers but no sign of a cucumber just the plant pictured. Any ideas what it is..... a weed? Thanks in advance.

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Re: Any ideas what this plant is?

Reply from Mrs. S. M. Bentley

Think it is a weed