Link to images of broccoli seedlings. https://www.backyardgardenlover.com/how-to-grow-broccoli/

Top photo – It’s hard to tell without seeing the whole plant. I’m taking a wild guess for now. Maybe something in the Erigeron? Perhaps Canadian horseweed (Erigeron canadensis)?. Click on images below to enlarge. If this isn’t that, please resubmit with photo of the whole plant & flowers if there are any. Middle photo- Please resubmit with more details; the whole plant & flowers if there are any. Bottom photo – Maybe something in the cabbage family? Perhaps broccoli, cauliflower, etc… As this grow more mature and you still don’t know please resubmit with photos. Best wishes! https://en.wikipedia.org/wiki/Erigeron_canadensis