The Six of Cups is the card of past, nostalgia, reunions. It is considered as one of the 'karmic' cards in Tarot, as some say it can show connections from past lives. The Nine of Cups is the symbol of emotional fulfillment. Regardless of his reputation as the "wish" card, the Nine of Cups - like all 9s- often leaves out the participation of others and focuses on the individual. That's why the Nine of Cups, in most cases, indicates situations that make us feel happy with who we are and what we have achieved. The combination of the Six of Cups and the Nine of Cups is about enjoying positive energies and/or a strong connection with another.
To understand the elemental relationships between the cards, we should always take into account their actual meaning. The elements of the cards are Water (Six of Cups) and Water (Nine of Cups). The elements are neutral and friendly to each other, but too much water can lead to passivity or inertia. The Six of Cups and the Nine of Cups can be a pleasant moment of joy and connection, but there's always the risk of over-indulgence or getting lost in memories of the past.