In the present age we are not thrown together by chance with other people. That the path of life brings us into contact with certain people and not with others depends upon the working out of individual karma. [….]
Think how much less karma had been accumulated in the earlier periods of earth evolution! With every incarnation fresh karma is made. At first, people had to meet under totally new conditions, with the possibility of forming fresh connections. But through repeated earth-lives we have gradually reached a point at which, as a general rule, we do not meet anyone with whom in former incarnations we have not shared this or that experience. And these experiences bring us into contact again with those who shared them. We meet other people as it would appear by chance but in reality because in former incarnations we had already met, and on the strength of this are brought together again.
Source: Rudolf Steiner – GA 168 – How Can the Destitution of Soul in Modern Times Be Overcome? / Social Understanding – Liberty of Thought – Knowledge of the Spirit – Zurich, October 10th, 1916