This is the myth where Rome originated. Is it even possible for a she-wolf to feed human babies? I don't know if someone had tried doing this but I think it is impossible as babies are very vulnerable to diseases.
I have a bachelor's on zoology so I can tell you that it isn't uncommon for mammals to sometimes suckle babies of a different species. I have read that in times before the advent of breast milk substitutes people would feed babies milk from any viable source; cows, sheep, goats, etc. Since infants receive valuable immunities from their mother's milk, these infants had an astoundingly high mortality rate but some did survive. And babies will suckle on ANYTHING so if a wolf's teat got near his mouth he would probably suckle on it. So it is possible however highly unlikely that this would work. It would require an extremely accommodating wolf and a lot of luck that the boys don't contract any viruses or bacteria. (unlikely in a forest) More than likely the wolf would have just classified the boys as "easy pickings" and eaten them.
Modern day tales of children raised by wolves do exist though. Having said that I can't remember if they involved actual suckling or not. I am nowhere near a scientist but I imagine it would be hard for a human baby to get perfect nutrition from the milk of another species.