My first guess would be basswood.

Sycamore

Sugarberry (Celtis)

Ding. Ding. arbordave gets it. The forests around here were logged maybe 60 yrs ago, and every basswood resprouted with at least 2 to sometimes 4 trunks. One just across my border stream died for some reason when I was first here, but 22 yrs later there are 4 slender sprouts from its base in rather deep shade that are now 50 ft tall. I posted a pic here some time ago of the dead original trunk that had been ravaged by a piliated woodpecker.

PS The one pictured above has 3 trunks, a shaded one just off to the right.