A mutt, squash are very promiscuos.

They look like pumpkin seedlings but i am not sure.

That looks very much like a weed that grows around here.
It is Common Mallow.

http://www.scottslawnservice.com/sls/templates/index.jsp?pageUrl=slscommonmallow

It looks like Mallow to me, too. It is super-duper invasive in my yard. An attractive plant, and the flowers are are pretty, too, but don't let it fool you. Let just one of of these suckers go to seed and you will have 500 million of them growing everywhere. Each root goes clear to china and if it breaks off...it just grows back. Every little root left in the ground grows a whole new plant. Can you tell, I don't like mallow? :)

Definitely Malva neglecta also called cheeses by the more polite. Also all parts are edible both raw or cooked. An Old World native originally.