It's not necessarily common, but it has happened in the past. Usually you don't see them quite so close to each other, however, and almost always one of them is a Cape Verde storm -- not the case here.

The record for overall storms at once is either 4 or 5; it occurred in 1995 and I want to say it is 4 with one dissipating or going extratropical early one day and another system forming later that same day. Don't hold me to that, though.