It happens after the long experience of love. When two individuals share so much about them that they know the other person completely. That much, that apart from flesh they can identify the soul of their beloved one. It happens when both of them reach that certain level of spirituality when just words are not the only medium to communicate. And they experience that completeness, when they experience their second half as not their second half but a unified whole. It happens, and it’s real. As Rumi said:
”Hidden from all I will speak to you without words.
No one but you will hear my story
Even if I tell it in the middle of the crowd.”