In astrology there is such a "crystal ball" type answer and that is with Chiron. Chiron is special and has some special answers to these important questions. You have to look for aspects between your Chiron and your partner's Venus first of all to see if you have a trine, conjunction, inconjunct or a linkage in the declinations. These aspects can pretty much tell you whether this person is a soul mate for you. Unfortunately, if you have an aspect such as square or opposition, it could indicate that there is a strong desire to become married but it is or could be "the impossible dream". Even if you do get married, there will always seem like there's something not quite right. Usually a high degree of fantasy, and perhaps having too high of expectations.

Now the one to really look out for is Saturn. This one can be mighty frustrating. You can have all the wonderful synastry in the world, but if Saturn is in a challenging aspect to your Chiron or vice versa then you have a problem. One or the other person will seemingly have control over the relationship and he or she could also in the long run break your heart. The aspects to look out for are the conjunction, inconjunct, square, opposition and in the declinations the contra parallel. Now the conjunction can also be a good thing too, it can mean a long term relationship, but the person who is the Saturn person still has some degree of control over the relationship in some way.

In the overall compatibility of your relationship this particular astrological element can help you to decide if there is long term potential. Especially look for these indicators if you are desiring to get married as this alone can help you to decide if this is the right person for you.

So, before you invest way too much time with the wrong person, or you feel this is the right person and just want some validation I would strongly check out these aspects for your long term love prospects.