The 7th house ruler in detriment or fall:
A planet in the sign opposite the sign of its exaltation is said to be in fall. Put simply, the planet loses its strength or influence. This can potentially imply a weakness or distress and disappointment pertaining to committed relationships or the partner themselves. When a planet has no dignity it is classified as, peregrine William Lilly stated in Christian astrology as, “wandering shiftlesly,” and he also often used peregrine planets to represent thieves. I am curious if a peregrine planet could there is a propensity to have others who maybe try to steal one’s spouse? Statistics and personal experiences often tend to indicate that even when a planet is in detriment or in fall, things can turn positively if there is mutual reception or positive aspects at play so don’t get too worried.
A dual body sign on the 7th house cusp: having gemini, sagittarius or Pisces ruling the cusp of the 7th house can allegedly indicate a potential for a spouse or the native to have a tendency to have more than one person that they are committed to or having relations with. It can indicate multiple marriages may occur in the native’s life. I suppose that this idea makes sense in some ways. Gemini represents the twins. The sign is often associated with people who have two different types of personalities, faces or those who lead dual lives. Pisces is represented by the two fish, I think you get the point though right?
Neptune contacting the 7th house ruler or Venus by progression, solar arc or transit: this can indicate infidelity coming into play for the native or already occurring. Adultery is ruled by venus, uranus and neptune according to Bill Rex whom authored the rulership book so I suppose it makes sense that the combination of these planets can manifest as infidelity in a relationship. However, as a professional astrologer I have seen neptune and venus create fairy tale relationships, love at first sight and magical romances. then again, I will also admit that I have seen these two combined in client’s charts creating issues with deception, lies (not necessarily always cheating but often lying).
Uranus contacting the 7th house ruler or Venus natally, in transit or by solar arc: I always imagine that the type of cheating associated with this combination is sudden, possibly shocking and typically short lived. Think along the lines of one night stands, short lived flings and unstable or unpredictable relationships. Uranus also rules separations and divorce so be prepared for that if you are cheating I guess. On the other hand uranus can electrify your relationship, making it more exciting, stimulating, unconventional or spontaneous.