Since the previously quoted Qur'aanic verse clarifies that human souls leave the body during sleep to roam about in the spiritual realm, and it has been established that they can meet the souls of the dead, then it is logical to assume that they are able to meet each other as well.
Imaam Ibnul Qayyim رحمه الله confirms this point and replies to the following oft-posed question of doubt: "How does a person during sleep 'see' himself conversing other living people, even though they are far away and awake - their souls having not left their bodies?" How do their souls "meet" per se?
Imaam Ibnul Qayyim رحمه الله answers that this phenomenon is either a likeness (mathal) made for the soul of the sleeper by the angel of visions or a result of sleeper's soul conversing with itself (hadeethu nafs). This "conversation" is illustrated in the images seen in his dreams.  
 Kitaab ar-Rooh, pp. 47-48.
 Abu Bilal Mustafa al-Kanadi رحمه الله: Mysteries of the Soul Expounded