This is a speculative post so please take it as no more than a suggestion for further research and meditation.
Human beings are social animals and this is just as true for souls in the spiritual world whence we originate as it is in this terrestrial world. It does not reflect the way we have evolved (modern science usually gets things back to front in this respect) but the way we are and the fact that we are created in the image of God whose nature is love which means relationship, communion and delight in sharing. God may be a solitary in essence (of course, he may not be if the Trinity has anything to say on the matter), but he is not in expression. That is why he creates and why the one becomes the many.
From various remarks the Masters made during the course of their instructions to me it seems that there are spiritual families just as there are earthly ones though, as one would expect, the spiritual ones are held together by even stronger bonds. It is not blood ties but spiritual ones that bind them and these are indestructible so long as a soul remains in existence. Whether these families come about from a shared spiritual parentage, I can't say. It seems possible they might but to know this one would have to know how souls actually are created, whether they have spiritual antecedents or come directly from God. My intuition is that we do have spiritual parents for it is clear that God frequently delegates. Of course, everything originally comes from him and we all have our direct inner link to him, his being is our being, but it may well be that there are intermediaries between the Creator and the individual soul whence the origin of spiritual families or group souls.
Spiritual families have a greater unity and similarity of being than earthly ones for they share the same nature to a greater degree. You might say they are formed from the same mould though this would not take away from the uniqueness and individuality of each member. But still they would share a similar spiritual quality of being as opposed to shape of nose or musical ability. In esoteric parlance, they would be on the same ray.
We all come from a spiritual world whence we 'descend' to this Earth and mortal life in order to learn the lessons needed to make us more effective co-creators with God in the unfolding and expression of manifested life. We are gods in the making, gods under our Creator, but most of us at the present stage have a long way to go to reach the fullness of our divine potential. It's possible that some may never reach it just as some seeds fail to sprout though perhaps these are recycled and given another chance to blossom either here or elsewhere. Patterns repeat themselves on every level and so it seems likely that within the spiritual families there are older and younger members, those who have been created earlier and unfolded more of their divine potential and those who still have a way to go.
Members of our family in this world may also be members of our spiritual group but they may not be. I would speculate that a real closeness indicates a spiritual connection while the feeling that, although that particular person is my brother or mother, I don't feel I have much in common with him or her indicates the opposite. But we are here to learn lessons so we may well find we are put with people with whom we have little rapport or even clash, the better to deal with aspects of our personality that are brought out by the experience.
It is not necessary to try to establish any contact with one's spiritual family while in the world. What is meant to be will happen. What is not, won't. The goal here is to establish a connection to God. Then, once we have done our earthly duty, we can return to our family in the higher worlds. As the Masters told me (slightly edited, though not to alter the sense), 'we look forward to being reunited in the heavenly plane which is your home'.
So live and work fully in this world. You are meant to be here so you should invest yourself completely in that task. No shirking or running away from it into dream worlds or fantasies! But then, when your work is done, you will return to the higher worlds to be greeted by souls you knew before, who you love and who love you as one of theirs.