World Layers

A single world has many ‘layers’. For example, take the DMCverse into account. There is not just one Dante, for there are many layers to this realm. One Dante might be a couple with Trish, while in another layer, another Dante has feelings for Lady. There is even a Dante that looks vastly different from the other, bearing dark hair as opposed to white. 
Simply put, one world has many different versions; some, probably identical to the other, some, varying greatly.