the composite vertex and composite node on the composite descendant gives a strong psychic and mental connection. with the vertex the partners usually have had, strange, other worldly experiences in their lives. many times this can make them feel like soul mates as the as both has felt these supra natural feelings or experiences.
but this is not a indication of a successful relationship by itself, because often the mental chaos that can result will destabilize a relationship. you need you look at the aspects in the composite to determine the nature of the relationship.
rahu