Hi Suzie,
From my experience... I would say it is possible for them to start teething that young.
I think Aidyn started developing his teething symptoms at around 3 months old, but his bottom 2 middle ones didn't come through until 5 months.
Apparently if the teeth come through really early, there is a possibility that they may go back under the gum again as well, and re-cut a few times. This happened to Christy's daughter Matilda.

Also, I'm not sure on this, but is there meant to be a certain order in which the teeth are meant to cut? Or is that just fiction? I always assumed it was bottom 2 middle, then top 2 middle, but would love to hear if other's babies have been different...?