If the personal planets - Sun, Moon, Mercury, Venus, and Mars and the Ascendant and the Ascendant lord in your chart conjunct the south node in the other person's chart or vice-versa then the relationship is karmic.
This kind of planetary alignment suggests the two of you were in a significant relationship, and there's still some unfinished work with regard to that relationship. Hence, the present situation has been created to enable you two to meet and complete the purpose of that relationship.The nature of the relationship depends on the personal planet conjunct with the south node.
For example, if Mars or Mercury is the planet, then the relationship could be that of siblings, comrades, friends, peers, competitors, or even adversaries.
If the planet is Venus, then it is very likely the two of you were a couple, lovers, or involved romantically in a previous life.
If the Sun is conjunct with the south node, then the relationship involves a male authority figure—such as a father or a boss.
With the Moon as the conjunction planet, the relationship involved a female authority figure in the family—such as a mother, a senior female relative, or a nurturer.
If it is the Ascendant or Ascendant lord, then the relationship could be with a guide, mentor, decision-maker, or someone in authority who had some level of control over the path your life would take.
This planetary placement occurs when the karmic relationship requires you and the other person to overcome your differences, learn to honour and respect each other, live in harmony, and, in the case of Venus, learn to love each other.