Many times, Sri Dasguptaji used to speak about the difference between the physical family and the spiritual family.
He used to always say that a Guru has two families with completely different relationship to him. The physical family who are heirs to the physical property alone. Their relationship is in the physical world, solely on the physical plane. They are heirs to the physical property which is their world……the physical world. Their relationship is not spiritual and is not based on spiritual “Sat Guru- disciple”. It is physical alone. It is “father and child” or “husband and spouse” and so forth.
It is a relationship on the physical plane alone.  Then there is the spiritual family, the spiritual children…the initiated disciples who my Master used to always tell us are the sole heirs to the spiritual property of the Guru.  Over and over he would speak of this …the spiritual children who are sole heirs to the spiritual property and the physical family who are the heirs to the physical property Their relationship is very different and he used to caution they should be kept separate.  They are two completely different worlds. The “Two Families” he used to tell us. ……the physical heirs and the spiritual heirs. They are separate.
The two don’t mix except on rare occasion when a physical child should become an initiated disciple of the Guru.In that case, then the relationship changes. In that event, the physical family relationship dies and is overshadowed by the spiritual relationship.  “Father” is no longer “father”. The physical relationship dies and is overtaken by the spiritual one. Father is no longer “father” but is now Sat Guru. The child is no longer a “physical son or daughter” but is now one of the disciples along with the other disciples and his status as such is not influenced at all by the fact that he is (was) a physical family member. In fact, that ceases. That stays completely out of it. He is now one of the spiritual children and like all the other disciples his status is determined solely by his spiritual performance and accomplishment…or lack of it……. whichever the case may be. There may be other of the spiritual children (disciples) who far surpass him on the spiritual path and who are very much his seniors. The Guru alone decides and picks his channels and spiritual successors and that is based on spiritual accomplishment alone. It is not a family title. Family ceases. Great Yogis have no attachment to family or caste or pride and so forth. Those things are part of the physical world left behind. They are not part of the spiritual world. The Illumined Yogis have no attachment to family or title or pride or caste or anything else of the physical world. They are long passed that, having left it all behind upon crossing the luminous shores of Samadhi
Lahiri Mahasay from Manu 149-150:
One who helps/ makes someone hear a little amount of Omkar - Sound, for the benefit of the aspirant at the time of giving Kriya - call and honor that person as
The one who is the giver of initiation and who disciplines for the sake of Kriya - even if he is a child, know him verily asfather.
~Lahiri Mahasaya (The Scriptural Commentaries of Yogiraj Sri SriShyama Charan Lahiri Mahasaya Volume 1 Yoga Niketan.)