The child is linked to their parent by biology. The body is a physical manifestation of the ancestral karma. This means biological triggers are set off similarly within a family, not always but often these are very similar.
Of course all of us humans develop along the same general lines. These are reflected in astrology: the transit of Saturn for example, especially the Saturn return. Astrology also points to natural affinities between people due to harmony between the planets of two people. Hinduism goes further by addressing these harmonies in terms of the elemental mix of the two people.
We can also be linked similarly on a psychic level. As it is true we tend to take birth with or in the family of those we have past karma with , we also link to others who we have karma with or have similar karmas. These are initially psychic bonds…they don’t have a biological basis but we naturally feel more affinity with these people.
So we all enter this matrix of factors when we take birth; it is not random. But there is a powerful variable factor…free will. We can choose to fight or cooperate with these forces as well as choose to break their hold on us. This is true for all human beings but it is very true in those who have entered the spiritual path. This is why sadhana and the influence of our guru can changes us fundamentally…because these break the matrix allowing new possibilities to manifest.
These principles are also active in the relationship between the guru and their disciple. The reason a teacher becomes our guru is there is one of the above affinities between the systems of the two. But in this case it is a psychic link. So the disciple shares in the guru’s state and the guru can enter into the psychic state of the disciple. That is how the guru knows how the disciple is doing.
This is now my experience. It is this psychic affinity with Bhagavan that carried me when my own system was weak. When I choose him as my guru and he accepted me, a psychic link was formed. He became my refuge and my boatman. It is this link that carried me to my goal. This is now my experience with those who come to me. I feel this happens naturally between all gurus and disciples.