Hello Astro Bunny:
First off, I do not buy into the asteroids, or the smaller. specialty planets. However, we do have enough information with the traditional planets and aspects to make an informed opinion.
The zero degrees of Gemini rising is always a red flag, unless you know for sure that the birth times of the couple are very accurate. Therefore, it could be late Taurus rising, or early Gemini.
In any event, in a "menage a trois" situation, you are symbolized by the 11th house of friends. Therefore, Mars in Gemini is your ruler.
It is found in the 1st house of the couple's personal outgoing image, so Mars in the 1st can indicate a strong sexual come on. However, since Mars is also in Gemini, opposite Uranus, and Neptune, and squaring Jupiter, this couple could well change their minds in a heart beat or even chicken out, without warning, so watch out.
Be careful with them, as they could become unreliable ?
The wife is always symbolized by the composite Moon, as are all females. The male is represented by the Sun in Leo. As Sun trines Uranus, he is outgoing and open-minded, sexually.
The Moon conjunct Saturn (representing the female) tends to be very loyal to the husband, no matter what ? And, the woman likes a lot of control over situations, especially bedroom matters and family matters.
With Moon and Saturn squaring Mercury in Virgo, this couple, it should also be noted, has different opinions and views over how the family and home should be shaped, but since the Moon is in the 7th house of Libra, she tends to go along with whatever the husband says, but she is very controlling and argumentative ?
As far as the menage goes, Moon conjunct Saturn tends to be very loyal and conservative, so if you do pursue this couple, it must be done over time and you must earn their trust, as the wife also tends to be rather paranoid about things.
I will predict it's not a good bet that you can pursuade the husband to leave his wife and live with you. The couple are attached for good, and when divorce happens, it will be very messy and it's not a good idea to stick around, as Moon = Saturn forms an unshakeable bond, so it's not easy to leave, even when the couple is finished.
The couple's main priority is home and family, and not even sex, so I would pass on this one, if I were you. However, its is possible that a short term relationship could happen.
Good luck !