Let's examine the houses ruled by Venus-the planet of relationships, from Scorpio(Ascendant, Sun or Moon).
Venus is the ruler of the 7th and 12th sign from Scorpio, combining the meaning of relationships with the meaning of the 7th and 12th houses. Translated: Scorpio's relationships are often with the purpose of not just sex, but a deeper commitment(7th-marriage, commitment). That is why Scorpios do not like superficial relationships! This is the good news!
The bad news is that Venus (love) is also the lord of their 12th house-which rules secrets and affairs(at the lower level)! Scorpio people, albeit inclined to committed and long lasting relationships(7th), can also be tempted into a secretive, private such liaisons.
Actually in ancient astrology the 12th house ruled sexual private pleasure, so for Scorpio it is of utmost importance to have a healthy and very rich sex life, which should be kept private (12th house) or else the marriage/long term relationship(7th house) will suffer through affairs, cheating or divorce(all of which are also ruled by the 12th house).
Unless both partners are committed to keeping a constant, satisfying and intensely romantic sexual practice, which is so hard to do, Scoprios are very likely to go into a 2nd and even 3rd marriage or marriage like relationship.
One way to keep this fairy-tale like sensuality in the relationship, is through arranging getaways in very relaxed, exotic or romantic environments(12th house) or through practicing less invasive and more spiritual sex(12th house)-like Karezza, Tantric embraces or gentle, slow love making, not focused on orgasm-this way the sexual passion between the couple is transformed into more spiritual, deep, tranformative bonding(12th house) and increases over time.
Rough/masculine/orgasm focused sex based on physical passions only, depletes the deep romantic bond between the couple and decreases with time. For Scorpio this leads to separations, divorces or problems in relationships.
This is the curse and the blessings of Scorpios-the sexual energy in relationships, when practiced with deep spiritual bonding, can lead to ecstatic states of emotional and psychological bonding, which no other Sign can do with such intensity, but if practices from the animal, selfish side only or blocked in some ways, will lead to undoing of their long term relationships.
The secret for marriage happiness for Scorpio is a regularly, deeply bonding spiritualized sex life focused on the sharing and giving in to the other, rather than selfish gratification. The sex life of Scorpio should be sacred and non-casual, then they will attract the best partner or improve their relationship.
Scorpio will often attract deeply sensual partners(Venus-the planet of sensuality rules their house of relationships-Taurus), who are also very attractive. But due to misuse of sexual energy(especially in the way western people do-for self gratification only) Scorpios often end up having secret relationships or more than one marriage.