As you know God speaks to us in various ways, including dreams and visions.  This could be a forthcoming premonition of someone who will be coming into your life and you will be quickened in your spirit as if you 'know' them.  But also be warned, God told us to test the spirits.  Use discernment and the guidance of the Holy Spirit of Truth.  As we have a deceptive foe who would love us to be entrapped or lead astray! Know the source and you will be o.k